feat: time tracking + billing (P1)

backend/internal/auth/context.go

@@ -9,19 +9,11 @@ import (
 type contextKey string
 
 const (
-<<<<<<< HEAD
-	userIDKey    contextKey = "user_id"
-	tenantIDKey  contextKey = "tenant_id"
-	ipKey        contextKey = "ip_address"
-	userAgentKey contextKey = "user_agent"
-||||||| 82878df
-	userIDKey   contextKey = "user_id"
-	tenantIDKey contextKey = "tenant_id"
-=======
 	userIDKey    contextKey = "user_id"
 	tenantIDKey  contextKey = "tenant_id"
 	userRoleKey  contextKey = "user_role"
->>>>>>> mai/pike/p0-role-based
+	ipKey        contextKey = "ip_address"
+	userAgentKey contextKey = "user_agent"
 )
 
 func ContextWithUserID(ctx context.Context, userID uuid.UUID) context.Context {
@@ -41,7 +33,15 @@ func TenantFromContext(ctx context.Context) (uuid.UUID, bool) {
 	id, ok := ctx.Value(tenantIDKey).(uuid.UUID)
 	return id, ok
 }
-<<<<<<< HEAD
+
+func ContextWithUserRole(ctx context.Context, role string) context.Context {
+	return context.WithValue(ctx, userRoleKey, role)
+}
+
+func UserRoleFromContext(ctx context.Context) string {
+	role, _ := ctx.Value(userRoleKey).(string)
+	return role
+}
 
 func ContextWithRequestInfo(ctx context.Context, ip, userAgent string) context.Context {
 	ctx = context.WithValue(ctx, ipKey, ip)
@@ -62,15 +62,3 @@ func UserAgentFromContext(ctx context.Context) *string {
 	}
 	return nil
 }
-||||||| 82878df
-=======
-
-func ContextWithUserRole(ctx context.Context, role string) context.Context {
-	return context.WithValue(ctx, userRoleKey, role)
-}
-
-func UserRoleFromContext(ctx context.Context) string {
-	role, _ := ctx.Value(userRoleKey).(string)
-	return role
-}
->>>>>>> mai/pike/p0-role-based

backend/internal/auth/middleware.go

@@ -35,36 +35,6 @@ func (m *Middleware) RequireAuth(next http.Handler) http.Handler {
 		}
 
 		ctx := ContextWithUserID(r.Context(), userID)
-<<<<<<< HEAD
-		// Tenant resolution is handled by TenantResolver middleware for scoped routes.
-		// Tenant management routes handle their own access control.
-||||||| 82878df
-
-		// Resolve tenant and role from user_tenants
-		var membership struct {
-			TenantID uuid.UUID `db:"tenant_id"`
-			Role     string    `db:"role"`
-		}
-		err = m.db.GetContext(r.Context(), &membership,
-			"SELECT tenant_id, role FROM user_tenants WHERE user_id = $1 LIMIT 1", userID)
-		if err != nil {
-			http.Error(w, "no tenant found for user", http.StatusForbidden)
-			return
-		}
-		ctx = ContextWithTenantID(ctx, membership.TenantID)
-		ctx = ContextWithUserRole(ctx, membership.Role)
-
-=======
-
-		// Resolve tenant from user_tenants
-		var tenantID uuid.UUID
-		err = m.db.GetContext(r.Context(), &tenantID,
-			"SELECT tenant_id FROM user_tenants WHERE user_id = $1 LIMIT 1", userID)
-		if err != nil {
-			http.Error(w, "no tenant found for user", http.StatusForbidden)
-			return
-		}
-		ctx = ContextWithTenantID(ctx, tenantID)
 
 		// Capture IP and user-agent for audit logging
 		ip := r.Header.Get("X-Forwarded-For")
@@ -73,7 +43,9 @@ func (m *Middleware) RequireAuth(next http.Handler) http.Handler {
 		}
 		ctx = ContextWithRequestInfo(ctx, ip, r.UserAgent())
 
->>>>>>> mai/knuth/p0-audit-trail-append
+		// Tenant resolution is handled by TenantResolver middleware for scoped routes.
+		// Tenant management routes handle their own access control.
+
 		next.ServeHTTP(w, r.WithContext(ctx))
 	})
 }

backend/internal/auth/tenant_resolver.go

@@ -12,12 +12,8 @@ import (
 // Defined as an interface to avoid circular dependency with services.
 type TenantLookup interface {
 	FirstTenantForUser(ctx context.Context, userID uuid.UUID) (*uuid.UUID, error)
-<<<<<<< HEAD
 	VerifyAccess(ctx context.Context, userID, tenantID uuid.UUID) (bool, error)
-||||||| 82878df
-=======
 	GetUserRole(ctx context.Context, userID, tenantID uuid.UUID) (string, error)
->>>>>>> mai/pike/p0-role-based
 }
 
 // TenantResolver is middleware that resolves the tenant from X-Tenant-ID header
@@ -46,38 +42,23 @@ func (tr *TenantResolver) Resolve(next http.Handler) http.Handler {
 				http.Error(w, `{"error":"invalid X-Tenant-ID"}`, http.StatusBadRequest)
 				return
 			}
-<<<<<<< HEAD
 
-			// Verify user has access to this tenant
+			// Verify user has access and get their role
-			hasAccess, err := tr.lookup.VerifyAccess(r.Context(), userID, parsed)
+			role, err := tr.lookup.GetUserRole(r.Context(), userID, parsed)
 			if err != nil {
 				slog.Error("tenant access check failed", "error", err, "user_id", userID, "tenant_id", parsed)
 				http.Error(w, `{"error":"internal error"}`, http.StatusInternalServerError)
 				return
 			}
-			if !hasAccess {
+			if role == "" {
 				http.Error(w, `{"error":"no access to tenant"}`, http.StatusForbidden)
 				return
 			}
 
-||||||| 82878df
-=======
-			// Verify user has access and get their role
-			role, err := tr.lookup.GetUserRole(r.Context(), userID, parsed)
-			if err != nil {
-				http.Error(w, "error checking tenant access", http.StatusInternalServerError)
-				return
-			}
-			if role == "" {
-				http.Error(w, "no access to this tenant", http.StatusForbidden)
-				return
-			}
->>>>>>> mai/pike/p0-role-based
 			tenantID = parsed
-			// Override the role from middleware with the correct one for this tenant
 			r = r.WithContext(ContextWithUserRole(r.Context(), role))
 		} else {
-			// Default to user's first tenant (role already set by middleware)
+			// Default to user's first tenant
 			first, err := tr.lookup.FirstTenantForUser(r.Context(), userID)
 			if err != nil {
 				slog.Error("failed to resolve default tenant", "error", err, "user_id", userID)
@@ -89,6 +70,15 @@ func (tr *TenantResolver) Resolve(next http.Handler) http.Handler {
 				return
 			}
 			tenantID = *first
+
+			// Also resolve role for default tenant
+			role, err := tr.lookup.GetUserRole(r.Context(), userID, tenantID)
+			if err != nil {
+				slog.Error("failed to get role for default tenant", "error", err, "user_id", userID, "tenant_id", tenantID)
+				http.Error(w, `{"error":"internal error"}`, http.StatusInternalServerError)
+				return
+			}
+			r = r.WithContext(ContextWithUserRole(r.Context(), role))
 		}
 
 		ctx := ContextWithTenantID(r.Context(), tenantID)

backend/internal/auth/tenant_resolver_test.go

@@ -10,49 +10,34 @@ import (
 )
 
 type mockTenantLookup struct {
-<<<<<<< HEAD
 	tenantID  *uuid.UUID
 	err       error
 	hasAccess bool
 	accessErr error
-||||||| 82878df
-	tenantID *uuid.UUID
-	err      error
-=======
-	tenantID *uuid.UUID
 	role      string
-	err      error
->>>>>>> mai/pike/p0-role-based
 }
 
 func (m *mockTenantLookup) FirstTenantForUser(ctx context.Context, userID uuid.UUID) (*uuid.UUID, error) {
 	return m.tenantID, m.err
 }
 
-<<<<<<< HEAD
 func (m *mockTenantLookup) VerifyAccess(ctx context.Context, userID, tenantID uuid.UUID) (bool, error) {
 	return m.hasAccess, m.accessErr
 }
 
-||||||| 82878df
-=======
 func (m *mockTenantLookup) GetUserRole(ctx context.Context, userID, tenantID uuid.UUID) (string, error) {
 	if m.role != "" {
 		return m.role, m.err
 	}
+	if m.hasAccess {
 		return "associate", m.err
 	}
+	return "", m.err
+}
 
->>>>>>> mai/pike/p0-role-based
 func TestTenantResolver_FromHeader(t *testing.T) {
 	tenantID := uuid.New()
-<<<<<<< HEAD
+	tr := NewTenantResolver(&mockTenantLookup{hasAccess: true, role: "partner"})
-	tr := NewTenantResolver(&mockTenantLookup{hasAccess: true})
-||||||| 82878df
-	tr := NewTenantResolver(&mockTenantLookup{})
-=======
-	tr := NewTenantResolver(&mockTenantLookup{role: "partner"})
->>>>>>> mai/pike/p0-role-based
 
 	var gotTenantID uuid.UUID
 	next := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
@@ -101,7 +86,7 @@ func TestTenantResolver_FromHeader_NoAccess(t *testing.T) {
 
 func TestTenantResolver_DefaultsToFirst(t *testing.T) {
 	tenantID := uuid.New()
-	tr := NewTenantResolver(&mockTenantLookup{tenantID: &tenantID})
+	tr := NewTenantResolver(&mockTenantLookup{tenantID: &tenantID, role: "owner"})
 
 	var gotTenantID uuid.UUID
 	next := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {

backend/internal/handlers/billing_rates.go

@@ -0,0 +1,66 @@
+package handlers
+
+import (
+	"encoding/json"
+	"net/http"
+
+	"mgit.msbls.de/m/KanzlAI-mGMT/internal/auth"
+	"mgit.msbls.de/m/KanzlAI-mGMT/internal/services"
+)
+
+type BillingRateHandler struct {
+	svc *services.BillingRateService
+}
+
+func NewBillingRateHandler(svc *services.BillingRateService) *BillingRateHandler {
+	return &BillingRateHandler{svc: svc}
+}
+
+// List handles GET /api/billing-rates
+func (h *BillingRateHandler) List(w http.ResponseWriter, r *http.Request) {
+	tenantID, ok := auth.TenantFromContext(r.Context())
+	if !ok {
+		writeError(w, http.StatusForbidden, "missing tenant")
+		return
+	}
+
+	rates, err := h.svc.List(r.Context(), tenantID)
+	if err != nil {
+		internalError(w, "failed to list billing rates", err)
+		return
+	}
+
+	writeJSON(w, http.StatusOK, map[string]any{"billing_rates": rates})
+}
+
+// Upsert handles PUT /api/billing-rates
+func (h *BillingRateHandler) Upsert(w http.ResponseWriter, r *http.Request) {
+	tenantID, ok := auth.TenantFromContext(r.Context())
+	if !ok {
+		writeError(w, http.StatusForbidden, "missing tenant")
+		return
+	}
+
+	var input services.UpsertBillingRateInput
+	if err := json.NewDecoder(r.Body).Decode(&input); err != nil {
+		writeError(w, http.StatusBadRequest, "invalid JSON body")
+		return
+	}
+
+	if input.Rate < 0 {
+		writeError(w, http.StatusBadRequest, "rate must be non-negative")
+		return
+	}
+	if input.ValidFrom == "" {
+		writeError(w, http.StatusBadRequest, "valid_from is required")
+		return
+	}
+
+	rate, err := h.svc.Upsert(r.Context(), tenantID, input)
+	if err != nil {
+		internalError(w, "failed to upsert billing rate", err)
+		return
+	}
+
+	writeJSON(w, http.StatusOK, rate)
+}

backend/internal/handlers/deadlines.go

@@ -198,18 +198,9 @@ func (h *DeadlineHandlers) Delete(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-<<<<<<< HEAD
-	if err := h.deadlines.Delete(tenantID, deadlineID); err != nil {
-		writeError(w, http.StatusNotFound, "deadline not found")
-||||||| 82878df
-	err = h.deadlines.Delete(tenantID, deadlineID)
-	if err != nil {
-		writeError(w, http.StatusNotFound, err.Error())
-=======
 	err = h.deadlines.Delete(r.Context(), tenantID, deadlineID)
 	if err != nil {
 		writeError(w, http.StatusNotFound, err.Error())
->>>>>>> mai/knuth/p0-audit-trail-append
 		return
 	}
 

backend/internal/handlers/invoices.go

@@ -0,0 +1,170 @@
+package handlers
+
+import (
+	"encoding/json"
+	"net/http"
+
+	"mgit.msbls.de/m/KanzlAI-mGMT/internal/auth"
+	"mgit.msbls.de/m/KanzlAI-mGMT/internal/services"
+
+	"github.com/google/uuid"
+)
+
+type InvoiceHandler struct {
+	svc *services.InvoiceService
+}
+
+func NewInvoiceHandler(svc *services.InvoiceService) *InvoiceHandler {
+	return &InvoiceHandler{svc: svc}
+}
+
+// List handles GET /api/invoices?case_id=&status=
+func (h *InvoiceHandler) List(w http.ResponseWriter, r *http.Request) {
+	tenantID, ok := auth.TenantFromContext(r.Context())
+	if !ok {
+		writeError(w, http.StatusForbidden, "missing tenant")
+		return
+	}
+
+	var caseID *uuid.UUID
+	if caseStr := r.URL.Query().Get("case_id"); caseStr != "" {
+		parsed, err := uuid.Parse(caseStr)
+		if err != nil {
+			writeError(w, http.StatusBadRequest, "invalid case_id")
+			return
+		}
+		caseID = &parsed
+	}
+
+	invoices, err := h.svc.List(r.Context(), tenantID, caseID, r.URL.Query().Get("status"))
+	if err != nil {
+		internalError(w, "failed to list invoices", err)
+		return
+	}
+
+	writeJSON(w, http.StatusOK, map[string]any{"invoices": invoices})
+}
+
+// Get handles GET /api/invoices/{id}
+func (h *InvoiceHandler) Get(w http.ResponseWriter, r *http.Request) {
+	tenantID, ok := auth.TenantFromContext(r.Context())
+	if !ok {
+		writeError(w, http.StatusForbidden, "missing tenant")
+		return
+	}
+
+	invoiceID, err := parsePathUUID(r, "id")
+	if err != nil {
+		writeError(w, http.StatusBadRequest, "invalid invoice ID")
+		return
+	}
+
+	inv, err := h.svc.GetByID(r.Context(), tenantID, invoiceID)
+	if err != nil {
+		internalError(w, "failed to get invoice", err)
+		return
+	}
+	if inv == nil {
+		writeError(w, http.StatusNotFound, "invoice not found")
+		return
+	}
+
+	writeJSON(w, http.StatusOK, inv)
+}
+
+// Create handles POST /api/invoices
+func (h *InvoiceHandler) Create(w http.ResponseWriter, r *http.Request) {
+	tenantID, ok := auth.TenantFromContext(r.Context())
+	if !ok {
+		writeError(w, http.StatusForbidden, "missing tenant")
+		return
+	}
+	userID, _ := auth.UserFromContext(r.Context())
+
+	var input services.CreateInvoiceInput
+	if err := json.NewDecoder(r.Body).Decode(&input); err != nil {
+		writeError(w, http.StatusBadRequest, "invalid JSON body")
+		return
+	}
+
+	if input.ClientName == "" {
+		writeError(w, http.StatusBadRequest, "client_name is required")
+		return
+	}
+	if input.CaseID == uuid.Nil {
+		writeError(w, http.StatusBadRequest, "case_id is required")
+		return
+	}
+
+	inv, err := h.svc.Create(r.Context(), tenantID, userID, input)
+	if err != nil {
+		internalError(w, "failed to create invoice", err)
+		return
+	}
+
+	writeJSON(w, http.StatusCreated, inv)
+}
+
+// Update handles PUT /api/invoices/{id}
+func (h *InvoiceHandler) Update(w http.ResponseWriter, r *http.Request) {
+	tenantID, ok := auth.TenantFromContext(r.Context())
+	if !ok {
+		writeError(w, http.StatusForbidden, "missing tenant")
+		return
+	}
+
+	invoiceID, err := parsePathUUID(r, "id")
+	if err != nil {
+		writeError(w, http.StatusBadRequest, "invalid invoice ID")
+		return
+	}
+
+	var input services.UpdateInvoiceInput
+	if err := json.NewDecoder(r.Body).Decode(&input); err != nil {
+		writeError(w, http.StatusBadRequest, "invalid JSON body")
+		return
+	}
+
+	inv, err := h.svc.Update(r.Context(), tenantID, invoiceID, input)
+	if err != nil {
+		writeError(w, http.StatusBadRequest, err.Error())
+		return
+	}
+
+	writeJSON(w, http.StatusOK, inv)
+}
+
+// UpdateStatus handles PATCH /api/invoices/{id}/status
+func (h *InvoiceHandler) UpdateStatus(w http.ResponseWriter, r *http.Request) {
+	tenantID, ok := auth.TenantFromContext(r.Context())
+	if !ok {
+		writeError(w, http.StatusForbidden, "missing tenant")
+		return
+	}
+
+	invoiceID, err := parsePathUUID(r, "id")
+	if err != nil {
+		writeError(w, http.StatusBadRequest, "invalid invoice ID")
+		return
+	}
+
+	var body struct {
+		Status string `json:"status"`
+	}
+	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
+		writeError(w, http.StatusBadRequest, "invalid JSON body")
+		return
+	}
+	if body.Status == "" {
+		writeError(w, http.StatusBadRequest, "status is required")
+		return
+	}
+
+	inv, err := h.svc.UpdateStatus(r.Context(), tenantID, invoiceID, body.Status)
+	if err != nil {
+		writeError(w, http.StatusBadRequest, err.Error())
+		return
+	}
+
+	writeJSON(w, http.StatusOK, inv)
+}

backend/internal/handlers/time_entries.go

@@ -0,0 +1,209 @@
+package handlers
+
+import (
+	"encoding/json"
+	"net/http"
+	"strconv"
+
+	"mgit.msbls.de/m/KanzlAI-mGMT/internal/auth"
+	"mgit.msbls.de/m/KanzlAI-mGMT/internal/services"
+
+	"github.com/google/uuid"
+)
+
+type TimeEntryHandler struct {
+	svc *services.TimeEntryService
+}
+
+func NewTimeEntryHandler(svc *services.TimeEntryService) *TimeEntryHandler {
+	return &TimeEntryHandler{svc: svc}
+}
+
+// ListForCase handles GET /api/cases/{id}/time-entries
+func (h *TimeEntryHandler) ListForCase(w http.ResponseWriter, r *http.Request) {
+	tenantID, ok := auth.TenantFromContext(r.Context())
+	if !ok {
+		writeError(w, http.StatusForbidden, "missing tenant")
+		return
+	}
+
+	caseID, err := parsePathUUID(r, "id")
+	if err != nil {
+		writeError(w, http.StatusBadRequest, "invalid case ID")
+		return
+	}
+
+	entries, err := h.svc.ListForCase(r.Context(), tenantID, caseID)
+	if err != nil {
+		internalError(w, "failed to list time entries", err)
+		return
+	}
+
+	writeJSON(w, http.StatusOK, map[string]any{"time_entries": entries})
+}
+
+// List handles GET /api/time-entries?case_id=&user_id=&from=&to=
+func (h *TimeEntryHandler) List(w http.ResponseWriter, r *http.Request) {
+	tenantID, ok := auth.TenantFromContext(r.Context())
+	if !ok {
+		writeError(w, http.StatusForbidden, "missing tenant")
+		return
+	}
+
+	limit, _ := strconv.Atoi(r.URL.Query().Get("limit"))
+	offset, _ := strconv.Atoi(r.URL.Query().Get("offset"))
+	limit, offset = clampPagination(limit, offset)
+
+	filter := services.TimeEntryFilter{
+		From:   r.URL.Query().Get("from"),
+		To:     r.URL.Query().Get("to"),
+		Limit:  limit,
+		Offset: offset,
+	}
+
+	if caseStr := r.URL.Query().Get("case_id"); caseStr != "" {
+		caseID, err := uuid.Parse(caseStr)
+		if err != nil {
+			writeError(w, http.StatusBadRequest, "invalid case_id")
+			return
+		}
+		filter.CaseID = &caseID
+	}
+	if userStr := r.URL.Query().Get("user_id"); userStr != "" {
+		userID, err := uuid.Parse(userStr)
+		if err != nil {
+			writeError(w, http.StatusBadRequest, "invalid user_id")
+			return
+		}
+		filter.UserID = &userID
+	}
+
+	entries, total, err := h.svc.List(r.Context(), tenantID, filter)
+	if err != nil {
+		internalError(w, "failed to list time entries", err)
+		return
+	}
+
+	writeJSON(w, http.StatusOK, map[string]any{
+		"time_entries": entries,
+		"total":        total,
+	})
+}
+
+// Create handles POST /api/cases/{id}/time-entries
+func (h *TimeEntryHandler) Create(w http.ResponseWriter, r *http.Request) {
+	tenantID, ok := auth.TenantFromContext(r.Context())
+	if !ok {
+		writeError(w, http.StatusForbidden, "missing tenant")
+		return
+	}
+	userID, _ := auth.UserFromContext(r.Context())
+
+	caseID, err := parsePathUUID(r, "id")
+	if err != nil {
+		writeError(w, http.StatusBadRequest, "invalid case ID")
+		return
+	}
+
+	var input services.CreateTimeEntryInput
+	if err := json.NewDecoder(r.Body).Decode(&input); err != nil {
+		writeError(w, http.StatusBadRequest, "invalid JSON body")
+		return
+	}
+	input.CaseID = caseID
+
+	if input.Description == "" {
+		writeError(w, http.StatusBadRequest, "description is required")
+		return
+	}
+	if input.DurationMinutes <= 0 {
+		writeError(w, http.StatusBadRequest, "duration_minutes must be positive")
+		return
+	}
+	if input.Date == "" {
+		writeError(w, http.StatusBadRequest, "date is required")
+		return
+	}
+
+	entry, err := h.svc.Create(r.Context(), tenantID, userID, input)
+	if err != nil {
+		internalError(w, "failed to create time entry", err)
+		return
+	}
+
+	writeJSON(w, http.StatusCreated, entry)
+}
+
+// Update handles PUT /api/time-entries/{id}
+func (h *TimeEntryHandler) Update(w http.ResponseWriter, r *http.Request) {
+	tenantID, ok := auth.TenantFromContext(r.Context())
+	if !ok {
+		writeError(w, http.StatusForbidden, "missing tenant")
+		return
+	}
+
+	entryID, err := parsePathUUID(r, "id")
+	if err != nil {
+		writeError(w, http.StatusBadRequest, "invalid time entry ID")
+		return
+	}
+
+	var input services.UpdateTimeEntryInput
+	if err := json.NewDecoder(r.Body).Decode(&input); err != nil {
+		writeError(w, http.StatusBadRequest, "invalid JSON body")
+		return
+	}
+
+	entry, err := h.svc.Update(r.Context(), tenantID, entryID, input)
+	if err != nil {
+		writeError(w, http.StatusBadRequest, err.Error())
+		return
+	}
+
+	writeJSON(w, http.StatusOK, entry)
+}
+
+// Delete handles DELETE /api/time-entries/{id}
+func (h *TimeEntryHandler) Delete(w http.ResponseWriter, r *http.Request) {
+	tenantID, ok := auth.TenantFromContext(r.Context())
+	if !ok {
+		writeError(w, http.StatusForbidden, "missing tenant")
+		return
+	}
+
+	entryID, err := parsePathUUID(r, "id")
+	if err != nil {
+		writeError(w, http.StatusBadRequest, "invalid time entry ID")
+		return
+	}
+
+	if err := h.svc.Delete(r.Context(), tenantID, entryID); err != nil {
+		writeError(w, http.StatusBadRequest, err.Error())
+		return
+	}
+
+	writeJSON(w, http.StatusOK, map[string]string{"status": "deleted"})
+}
+
+// Summary handles GET /api/time-entries/summary?group_by=case|user|month&from=&to=
+func (h *TimeEntryHandler) Summary(w http.ResponseWriter, r *http.Request) {
+	tenantID, ok := auth.TenantFromContext(r.Context())
+	if !ok {
+		writeError(w, http.StatusForbidden, "missing tenant")
+		return
+	}
+
+	groupBy := r.URL.Query().Get("group_by")
+	if groupBy == "" {
+		groupBy = "case"
+	}
+
+	summaries, err := h.svc.Summary(r.Context(), tenantID, groupBy,
+		r.URL.Query().Get("from"), r.URL.Query().Get("to"))
+	if err != nil {
+		internalError(w, "failed to get summary", err)
+		return
+	}
+
+	writeJSON(w, http.StatusOK, map[string]any{"summary": summaries})
+}

backend/internal/models/billing_rate.go

@@ -0,0 +1,18 @@
+package models
+
+import (
+	"time"
+
+	"github.com/google/uuid"
+)
+
+type BillingRate struct {
+	ID        uuid.UUID  `db:"id" json:"id"`
+	TenantID  uuid.UUID  `db:"tenant_id" json:"tenant_id"`
+	UserID    *uuid.UUID `db:"user_id" json:"user_id,omitempty"`
+	Rate      float64    `db:"rate" json:"rate"`
+	Currency  string     `db:"currency" json:"currency"`
+	ValidFrom string     `db:"valid_from" json:"valid_from"`
+	ValidTo   *string    `db:"valid_to" json:"valid_to,omitempty"`
+	CreatedAt time.Time  `db:"created_at" json:"created_at"`
+}

backend/internal/models/invoice.go

@@ -0,0 +1,38 @@
+package models
+
+import (
+	"encoding/json"
+	"time"
+
+	"github.com/google/uuid"
+)
+
+type Invoice struct {
+	ID            uuid.UUID       `db:"id" json:"id"`
+	TenantID      uuid.UUID       `db:"tenant_id" json:"tenant_id"`
+	CaseID        uuid.UUID       `db:"case_id" json:"case_id"`
+	InvoiceNumber string          `db:"invoice_number" json:"invoice_number"`
+	ClientName    string          `db:"client_name" json:"client_name"`
+	ClientAddress *string         `db:"client_address" json:"client_address,omitempty"`
+	Items         json.RawMessage `db:"items" json:"items"`
+	Subtotal      float64         `db:"subtotal" json:"subtotal"`
+	TaxRate       float64         `db:"tax_rate" json:"tax_rate"`
+	TaxAmount     float64         `db:"tax_amount" json:"tax_amount"`
+	Total         float64         `db:"total" json:"total"`
+	Status        string          `db:"status" json:"status"`
+	IssuedAt      *string         `db:"issued_at" json:"issued_at,omitempty"`
+	DueAt         *string         `db:"due_at" json:"due_at,omitempty"`
+	PaidAt        *time.Time      `db:"paid_at" json:"paid_at,omitempty"`
+	Notes         *string         `db:"notes" json:"notes,omitempty"`
+	CreatedBy     uuid.UUID       `db:"created_by" json:"created_by"`
+	CreatedAt     time.Time       `db:"created_at" json:"created_at"`
+	UpdatedAt     time.Time       `db:"updated_at" json:"updated_at"`
+}
+
+type InvoiceItem struct {
+	Description     string  `json:"description"`
+	DurationMinutes int     `json:"duration_minutes,omitempty"`
+	HourlyRate      float64 `json:"hourly_rate,omitempty"`
+	Amount          float64 `json:"amount"`
+	TimeEntryID     *string `json:"time_entry_id,omitempty"`
+}

backend/internal/models/time_entry.go

@@ -0,0 +1,24 @@
+package models
+
+import (
+	"time"
+
+	"github.com/google/uuid"
+)
+
+type TimeEntry struct {
+	ID              uuid.UUID  `db:"id" json:"id"`
+	TenantID        uuid.UUID  `db:"tenant_id" json:"tenant_id"`
+	CaseID          uuid.UUID  `db:"case_id" json:"case_id"`
+	UserID          uuid.UUID  `db:"user_id" json:"user_id"`
+	Date            string     `db:"date" json:"date"`
+	DurationMinutes int        `db:"duration_minutes" json:"duration_minutes"`
+	Description     string     `db:"description" json:"description"`
+	Activity        *string    `db:"activity" json:"activity,omitempty"`
+	Billable        bool       `db:"billable" json:"billable"`
+	Billed          bool       `db:"billed" json:"billed"`
+	InvoiceID       *uuid.UUID `db:"invoice_id" json:"invoice_id,omitempty"`
+	HourlyRate      *float64   `db:"hourly_rate" json:"hourly_rate,omitempty"`
+	CreatedAt       time.Time  `db:"created_at" json:"created_at"`
+	UpdatedAt       time.Time  `db:"updated_at" json:"updated_at"`
+}

backend/internal/router/router.go

@@ -29,14 +29,11 @@ func New(db *sqlx.DB, authMW *auth.Middleware, cfg *config.Config, calDAVSvc *se
 	deadlineRuleSvc := services.NewDeadlineRuleService(db)
 	calculator := services.NewDeadlineCalculator(holidaySvc)
 	storageCli := services.NewStorageClient(cfg.SupabaseURL, cfg.SupabaseServiceKey)
-<<<<<<< HEAD
 	documentSvc := services.NewDocumentService(db, storageCli, auditSvc)
-||||||| 82878df
-	documentSvc := services.NewDocumentService(db, storageCli)
-=======
-	documentSvc := services.NewDocumentService(db, storageCli)
 	assignmentSvc := services.NewCaseAssignmentService(db)
->>>>>>> mai/pike/p0-role-based
+	timeEntrySvc := services.NewTimeEntryService(db, auditSvc)
+	billingRateSvc := services.NewBillingRateService(db, auditSvc)
+	invoiceSvc := services.NewInvoiceService(db, auditSvc)
 
 	// AI service (optional — only if API key is configured)
 	var aiH *handlers.AIHandler
@@ -71,6 +68,9 @@ func New(db *sqlx.DB, authMW *auth.Middleware, cfg *config.Config, calDAVSvc *se
 	eventH := handlers.NewCaseEventHandler(db)
 	docH := handlers.NewDocumentHandler(documentSvc)
 	assignmentH := handlers.NewCaseAssignmentHandler(assignmentSvc)
+	timeEntryH := handlers.NewTimeEntryHandler(timeEntrySvc)
+	billingRateH := handlers.NewBillingRateHandler(billingRateSvc)
+	invoiceH := handlers.NewInvoiceHandler(invoiceSvc)
 
 	// Public routes
 	mux.HandleFunc("GET /health", handleHealth(db))
@@ -112,7 +112,7 @@ func New(db *sqlx.DB, authMW *auth.Middleware, cfg *config.Config, calDAVSvc *se
 	scoped.HandleFunc("GET /api/cases", caseH.List)
 	scoped.HandleFunc("POST /api/cases", perm(auth.PermCreateCase, caseH.Create))
 	scoped.HandleFunc("GET /api/cases/{id}", caseH.Get)
-	scoped.HandleFunc("PUT /api/cases/{id}", caseH.Update)    // case-level access checked in handler
+	scoped.HandleFunc("PUT /api/cases/{id}", caseH.Update)
 	scoped.HandleFunc("DELETE /api/cases/{id}", perm(auth.PermCreateCase, caseH.Delete))
 
 	// Parties — same access as case editing
@@ -162,21 +162,15 @@ func New(db *sqlx.DB, authMW *auth.Middleware, cfg *config.Config, calDAVSvc *se
 	// Dashboard — all can view
 	scoped.HandleFunc("GET /api/dashboard", dashboardH.Get)
 
-<<<<<<< HEAD
+	// Audit log — view requires PermViewAuditLog
-	// Audit log
+	scoped.HandleFunc("GET /api/audit-log", perm(auth.PermViewAuditLog, auditH.List))
-	scoped.HandleFunc("GET /api/audit-log", auditH.List)
 
-	// Documents
-||||||| 82878df
-	// Documents
-=======
 	// Documents — all can upload, delete checked in handler (own vs all)
->>>>>>> mai/pike/p0-role-based
 	scoped.HandleFunc("GET /api/cases/{id}/documents", docH.ListByCase)
 	scoped.HandleFunc("POST /api/cases/{id}/documents", perm(auth.PermUploadDocuments, docH.Upload))
 	scoped.HandleFunc("GET /api/documents/{docId}", docH.Download)
 	scoped.HandleFunc("GET /api/documents/{docId}/meta", docH.GetMeta)
-	scoped.HandleFunc("DELETE /api/documents/{docId}", docH.Delete) // permission check inside handler
+	scoped.HandleFunc("DELETE /api/documents/{docId}", docH.Delete)
 
 	// AI endpoints (rate limited: 5 req/min burst 10 per IP)
 	if aiH != nil {
@@ -185,7 +179,6 @@ func New(db *sqlx.DB, authMW *auth.Middleware, cfg *config.Config, calDAVSvc *se
 		scoped.HandleFunc("POST /api/ai/summarize-case", perm(auth.PermAIExtraction, aiLimiter.LimitFunc(aiH.SummarizeCase)))
 	}
 
-<<<<<<< HEAD
 	// Notifications
 	if notifH != nil {
 		scoped.HandleFunc("GET /api/notifications", notifH.List)
@@ -196,18 +189,32 @@ func New(db *sqlx.DB, authMW *auth.Middleware, cfg *config.Config, calDAVSvc *se
 		scoped.HandleFunc("PUT /api/notification-preferences", notifH.UpdatePreferences)
 	}
 
-	// CalDAV sync endpoints
-||||||| 82878df
-	// CalDAV sync endpoints
-=======
 	// CalDAV sync endpoints — settings permission required
->>>>>>> mai/pike/p0-role-based
 	if calDAVSvc != nil {
 		calDAVH := handlers.NewCalDAVHandler(calDAVSvc)
 		scoped.HandleFunc("POST /api/caldav/sync", perm(auth.PermManageSettings, calDAVH.TriggerSync))
 		scoped.HandleFunc("GET /api/caldav/status", calDAVH.GetStatus)
 	}
 
+	// Time entries — billing permission for create/update/delete
+	scoped.HandleFunc("GET /api/cases/{id}/time-entries", timeEntryH.ListForCase)
+	scoped.HandleFunc("POST /api/cases/{id}/time-entries", perm(auth.PermManageBilling, timeEntryH.Create))
+	scoped.HandleFunc("GET /api/time-entries", timeEntryH.List)
+	scoped.HandleFunc("GET /api/time-entries/summary", perm(auth.PermManageBilling, timeEntryH.Summary))
+	scoped.HandleFunc("PUT /api/time-entries/{id}", perm(auth.PermManageBilling, timeEntryH.Update))
+	scoped.HandleFunc("DELETE /api/time-entries/{id}", perm(auth.PermManageBilling, timeEntryH.Delete))
+
+	// Billing rates — billing permission required
+	scoped.HandleFunc("GET /api/billing-rates", perm(auth.PermManageBilling, billingRateH.List))
+	scoped.HandleFunc("PUT /api/billing-rates", perm(auth.PermManageBilling, billingRateH.Upsert))
+
+	// Invoices — billing permission required
+	scoped.HandleFunc("GET /api/invoices", perm(auth.PermManageBilling, invoiceH.List))
+	scoped.HandleFunc("POST /api/invoices", perm(auth.PermManageBilling, invoiceH.Create))
+	scoped.HandleFunc("GET /api/invoices/{id}", perm(auth.PermManageBilling, invoiceH.Get))
+	scoped.HandleFunc("PUT /api/invoices/{id}", perm(auth.PermManageBilling, invoiceH.Update))
+	scoped.HandleFunc("PATCH /api/invoices/{id}/status", perm(auth.PermManageBilling, invoiceH.UpdateStatus))
+
 	// Wire: auth -> tenant routes go directly, scoped routes get tenant resolver
 	api.Handle("/api/", tenantResolver.Resolve(scoped))
 

backend/internal/services/billing_rate_service.go

@@ -0,0 +1,88 @@
+package services
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/google/uuid"
+	"github.com/jmoiron/sqlx"
+
+	"mgit.msbls.de/m/KanzlAI-mGMT/internal/models"
+)
+
+type BillingRateService struct {
+	db    *sqlx.DB
+	audit *AuditService
+}
+
+func NewBillingRateService(db *sqlx.DB, audit *AuditService) *BillingRateService {
+	return &BillingRateService{db: db, audit: audit}
+}
+
+type UpsertBillingRateInput struct {
+	UserID    *uuid.UUID `json:"user_id,omitempty"`
+	Rate      float64    `json:"rate"`
+	Currency  string     `json:"currency"`
+	ValidFrom string     `json:"valid_from"`
+	ValidTo   *string    `json:"valid_to,omitempty"`
+}
+
+func (s *BillingRateService) List(ctx context.Context, tenantID uuid.UUID) ([]models.BillingRate, error) {
+	var rates []models.BillingRate
+	err := s.db.SelectContext(ctx, &rates,
+		`SELECT id, tenant_id, user_id, rate, currency, valid_from, valid_to, created_at
+		 FROM billing_rates
+		 WHERE tenant_id = $1
+		 ORDER BY valid_from DESC, user_id NULLS LAST`,
+		tenantID)
+	if err != nil {
+		return nil, fmt.Errorf("list billing rates: %w", err)
+	}
+	return rates, nil
+}
+
+func (s *BillingRateService) Upsert(ctx context.Context, tenantID uuid.UUID, input UpsertBillingRateInput) (*models.BillingRate, error) {
+	if input.Currency == "" {
+		input.Currency = "EUR"
+	}
+
+	// Close any existing open-ended rate for this user
+	_, err := s.db.ExecContext(ctx,
+		`UPDATE billing_rates SET valid_to = $3
+		 WHERE tenant_id = $1
+		 AND (($2::uuid IS NULL AND user_id IS NULL) OR user_id = $2)
+		 AND valid_to IS NULL
+		 AND valid_from < $3`,
+		tenantID, input.UserID, input.ValidFrom)
+	if err != nil {
+		return nil, fmt.Errorf("close existing rate: %w", err)
+	}
+
+	var rate models.BillingRate
+	err = s.db.QueryRowxContext(ctx,
+		`INSERT INTO billing_rates (tenant_id, user_id, rate, currency, valid_from, valid_to)
+		 VALUES ($1, $2, $3, $4, $5, $6)
+		 RETURNING id, tenant_id, user_id, rate, currency, valid_from, valid_to, created_at`,
+		tenantID, input.UserID, input.Rate, input.Currency, input.ValidFrom, input.ValidTo,
+	).StructScan(&rate)
+	if err != nil {
+		return nil, fmt.Errorf("upsert billing rate: %w", err)
+	}
+
+	s.audit.Log(ctx, "create", "billing_rate", &rate.ID, nil, rate)
+	return &rate, nil
+}
+
+func (s *BillingRateService) GetCurrentRate(ctx context.Context, tenantID uuid.UUID, userID uuid.UUID, date string) (*float64, error) {
+	var rate float64
+	err := s.db.GetContext(ctx, &rate,
+		`SELECT rate FROM billing_rates
+		 WHERE tenant_id = $1 AND (user_id = $2 OR user_id IS NULL)
+		 AND valid_from <= $3 AND (valid_to IS NULL OR valid_to >= $3)
+		 ORDER BY user_id NULLS LAST LIMIT 1`,
+		tenantID, userID, date)
+	if err != nil {
+		return nil, err
+	}
+	return &rate, nil
+}

backend/internal/services/invoice_service.go

@@ -0,0 +1,292 @@
+package services
+
+import (
+	"context"
+	"database/sql"
+	"encoding/json"
+	"fmt"
+	"time"
+
+	"github.com/google/uuid"
+	"github.com/jmoiron/sqlx"
+
+	"mgit.msbls.de/m/KanzlAI-mGMT/internal/models"
+)
+
+type InvoiceService struct {
+	db    *sqlx.DB
+	audit *AuditService
+}
+
+func NewInvoiceService(db *sqlx.DB, audit *AuditService) *InvoiceService {
+	return &InvoiceService{db: db, audit: audit}
+}
+
+type CreateInvoiceInput struct {
+	CaseID        uuid.UUID             `json:"case_id"`
+	ClientName    string                `json:"client_name"`
+	ClientAddress *string               `json:"client_address,omitempty"`
+	Items         []models.InvoiceItem  `json:"items"`
+	TaxRate       *float64              `json:"tax_rate,omitempty"`
+	IssuedAt      *string               `json:"issued_at,omitempty"`
+	DueAt         *string               `json:"due_at,omitempty"`
+	Notes         *string               `json:"notes,omitempty"`
+	TimeEntryIDs  []uuid.UUID           `json:"time_entry_ids,omitempty"`
+}
+
+type UpdateInvoiceInput struct {
+	ClientName    *string               `json:"client_name,omitempty"`
+	ClientAddress *string               `json:"client_address,omitempty"`
+	Items         []models.InvoiceItem  `json:"items,omitempty"`
+	TaxRate       *float64              `json:"tax_rate,omitempty"`
+	IssuedAt      *string               `json:"issued_at,omitempty"`
+	DueAt         *string               `json:"due_at,omitempty"`
+	Notes         *string               `json:"notes,omitempty"`
+}
+
+const invoiceCols = `id, tenant_id, case_id, invoice_number, client_name, client_address,
+	items, subtotal, tax_rate, tax_amount, total, status, issued_at, due_at, paid_at, notes,
+	created_by, created_at, updated_at`
+
+func (s *InvoiceService) List(ctx context.Context, tenantID uuid.UUID, caseID *uuid.UUID, status string) ([]models.Invoice, error) {
+	where := "WHERE tenant_id = $1"
+	args := []any{tenantID}
+	argIdx := 2
+
+	if caseID != nil {
+		where += fmt.Sprintf(" AND case_id = $%d", argIdx)
+		args = append(args, *caseID)
+		argIdx++
+	}
+	if status != "" {
+		where += fmt.Sprintf(" AND status = $%d", argIdx)
+		args = append(args, status)
+		argIdx++
+	}
+
+	var invoices []models.Invoice
+	err := s.db.SelectContext(ctx, &invoices,
+		fmt.Sprintf("SELECT %s FROM invoices %s ORDER BY created_at DESC", invoiceCols, where),
+		args...)
+	if err != nil {
+		return nil, fmt.Errorf("list invoices: %w", err)
+	}
+	return invoices, nil
+}
+
+func (s *InvoiceService) GetByID(ctx context.Context, tenantID, invoiceID uuid.UUID) (*models.Invoice, error) {
+	var inv models.Invoice
+	err := s.db.GetContext(ctx, &inv,
+		`SELECT `+invoiceCols+` FROM invoices WHERE tenant_id = $1 AND id = $2`,
+		tenantID, invoiceID)
+	if err == sql.ErrNoRows {
+		return nil, nil
+	}
+	if err != nil {
+		return nil, fmt.Errorf("get invoice: %w", err)
+	}
+	return &inv, nil
+}
+
+func (s *InvoiceService) Create(ctx context.Context, tenantID, userID uuid.UUID, input CreateInvoiceInput) (*models.Invoice, error) {
+	tx, err := s.db.BeginTxx(ctx, nil)
+	if err != nil {
+		return nil, fmt.Errorf("begin tx: %w", err)
+	}
+	defer tx.Rollback()
+
+	// Generate invoice number: RE-YYYY-NNN
+	year := time.Now().Year()
+	var seq int
+	err = tx.GetContext(ctx, &seq,
+		`SELECT COUNT(*) + 1 FROM invoices WHERE tenant_id = $1 AND invoice_number LIKE $2`,
+		tenantID, fmt.Sprintf("RE-%d-%%", year))
+	if err != nil {
+		return nil, fmt.Errorf("generate invoice number: %w", err)
+	}
+	invoiceNumber := fmt.Sprintf("RE-%d-%03d", year, seq)
+
+	// Calculate totals
+	taxRate := 19.00
+	if input.TaxRate != nil {
+		taxRate = *input.TaxRate
+	}
+
+	var subtotal float64
+	for _, item := range input.Items {
+		subtotal += item.Amount
+	}
+	taxAmount := subtotal * taxRate / 100
+	total := subtotal + taxAmount
+
+	itemsJSON, err := json.Marshal(input.Items)
+	if err != nil {
+		return nil, fmt.Errorf("marshal items: %w", err)
+	}
+
+	var inv models.Invoice
+	err = tx.QueryRowxContext(ctx,
+		`INSERT INTO invoices (tenant_id, case_id, invoice_number, client_name, client_address,
+			items, subtotal, tax_rate, tax_amount, total, issued_at, due_at, notes, created_by)
+		 VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14)
+		 RETURNING `+invoiceCols,
+		tenantID, input.CaseID, invoiceNumber, input.ClientName, input.ClientAddress,
+		itemsJSON, subtotal, taxRate, taxAmount, total, input.IssuedAt, input.DueAt, input.Notes, userID,
+	).StructScan(&inv)
+	if err != nil {
+		return nil, fmt.Errorf("create invoice: %w", err)
+	}
+
+	// Mark linked time entries as billed
+	if len(input.TimeEntryIDs) > 0 {
+		query, args, err := sqlx.In(
+			`UPDATE time_entries SET billed = true, invoice_id = ? WHERE tenant_id = ? AND id IN (?)`,
+			inv.ID, tenantID, input.TimeEntryIDs)
+		if err != nil {
+			return nil, fmt.Errorf("build time entry update: %w", err)
+		}
+		query = tx.Rebind(query)
+		_, err = tx.ExecContext(ctx, query, args...)
+		if err != nil {
+			return nil, fmt.Errorf("mark time entries billed: %w", err)
+		}
+	}
+
+	if err := tx.Commit(); err != nil {
+		return nil, fmt.Errorf("commit: %w", err)
+	}
+
+	s.audit.Log(ctx, "create", "invoice", &inv.ID, nil, inv)
+	return &inv, nil
+}
+
+func (s *InvoiceService) Update(ctx context.Context, tenantID, invoiceID uuid.UUID, input UpdateInvoiceInput) (*models.Invoice, error) {
+	old, err := s.GetByID(ctx, tenantID, invoiceID)
+	if err != nil {
+		return nil, err
+	}
+	if old == nil {
+		return nil, fmt.Errorf("invoice not found")
+	}
+	if old.Status != "draft" {
+		return nil, fmt.Errorf("can only update draft invoices")
+	}
+
+	// Recalculate totals if items changed
+	var itemsJSON json.RawMessage
+	var subtotal float64
+	taxRate := old.TaxRate
+
+	if input.Items != nil {
+		for _, item := range input.Items {
+			subtotal += item.Amount
+		}
+		itemsJSON, _ = json.Marshal(input.Items)
+	}
+	if input.TaxRate != nil {
+		taxRate = *input.TaxRate
+	}
+
+	if input.Items != nil {
+		taxAmount := subtotal * taxRate / 100
+		total := subtotal + taxAmount
+
+		var inv models.Invoice
+		err = s.db.QueryRowxContext(ctx,
+			`UPDATE invoices SET
+				client_name = COALESCE($3, client_name),
+				client_address = COALESCE($4, client_address),
+				items = $5,
+				subtotal = $6,
+				tax_rate = $7,
+				tax_amount = $8,
+				total = $9,
+				issued_at = COALESCE($10, issued_at),
+				due_at = COALESCE($11, due_at),
+				notes = COALESCE($12, notes),
+				updated_at = now()
+			 WHERE tenant_id = $1 AND id = $2
+			 RETURNING `+invoiceCols,
+			tenantID, invoiceID, input.ClientName, input.ClientAddress,
+			itemsJSON, subtotal, taxRate, subtotal*taxRate/100, total,
+			input.IssuedAt, input.DueAt, input.Notes,
+		).StructScan(&inv)
+		if err != nil {
+			return nil, fmt.Errorf("update invoice: %w", err)
+		}
+		s.audit.Log(ctx, "update", "invoice", &inv.ID, old, inv)
+		return &inv, nil
+	}
+
+	// Update without changing items
+	var inv models.Invoice
+	err = s.db.QueryRowxContext(ctx,
+		`UPDATE invoices SET
+			client_name = COALESCE($3, client_name),
+			client_address = COALESCE($4, client_address),
+			tax_rate = COALESCE($5, tax_rate),
+			issued_at = COALESCE($6, issued_at),
+			due_at = COALESCE($7, due_at),
+			notes = COALESCE($8, notes),
+			updated_at = now()
+		 WHERE tenant_id = $1 AND id = $2
+		 RETURNING `+invoiceCols,
+		tenantID, invoiceID, input.ClientName, input.ClientAddress,
+		input.TaxRate, input.IssuedAt, input.DueAt, input.Notes,
+	).StructScan(&inv)
+	if err != nil {
+		return nil, fmt.Errorf("update invoice: %w", err)
+	}
+
+	s.audit.Log(ctx, "update", "invoice", &inv.ID, old, inv)
+	return &inv, nil
+}
+
+func (s *InvoiceService) UpdateStatus(ctx context.Context, tenantID, invoiceID uuid.UUID, newStatus string) (*models.Invoice, error) {
+	old, err := s.GetByID(ctx, tenantID, invoiceID)
+	if err != nil {
+		return nil, err
+	}
+	if old == nil {
+		return nil, fmt.Errorf("invoice not found")
+	}
+
+	// Validate transitions
+	validTransitions := map[string][]string{
+		"draft":     {"sent", "cancelled"},
+		"sent":      {"paid", "cancelled"},
+		"paid":      {},
+		"cancelled": {},
+	}
+	allowed := validTransitions[old.Status]
+	valid := false
+	for _, s := range allowed {
+		if s == newStatus {
+			valid = true
+			break
+		}
+	}
+	if !valid {
+		return nil, fmt.Errorf("invalid status transition from %s to %s", old.Status, newStatus)
+	}
+
+	var paidAt *time.Time
+	if newStatus == "paid" {
+		now := time.Now()
+		paidAt = &now
+	}
+
+	var inv models.Invoice
+	err = s.db.QueryRowxContext(ctx,
+		`UPDATE invoices SET status = $3, paid_at = COALESCE($4, paid_at), updated_at = now()
+		 WHERE tenant_id = $1 AND id = $2
+		 RETURNING `+invoiceCols,
+		tenantID, invoiceID, newStatus, paidAt,
+	).StructScan(&inv)
+	if err != nil {
+		return nil, fmt.Errorf("update invoice status: %w", err)
+	}
+
+	s.audit.Log(ctx, "update", "invoice", &inv.ID, old, inv)
+	return &inv, nil
+}

backend/internal/services/time_entry_service.go

@@ -0,0 +1,276 @@
+package services
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+
+	"github.com/google/uuid"
+	"github.com/jmoiron/sqlx"
+
+	"mgit.msbls.de/m/KanzlAI-mGMT/internal/models"
+)
+
+type TimeEntryService struct {
+	db    *sqlx.DB
+	audit *AuditService
+}
+
+func NewTimeEntryService(db *sqlx.DB, audit *AuditService) *TimeEntryService {
+	return &TimeEntryService{db: db, audit: audit}
+}
+
+type CreateTimeEntryInput struct {
+	CaseID          uuid.UUID `json:"case_id"`
+	Date            string    `json:"date"`
+	DurationMinutes int       `json:"duration_minutes"`
+	Description     string    `json:"description"`
+	Activity        *string   `json:"activity,omitempty"`
+	Billable        *bool     `json:"billable,omitempty"`
+	HourlyRate      *float64  `json:"hourly_rate,omitempty"`
+}
+
+type UpdateTimeEntryInput struct {
+	Date            *string  `json:"date,omitempty"`
+	DurationMinutes *int     `json:"duration_minutes,omitempty"`
+	Description     *string  `json:"description,omitempty"`
+	Activity        *string  `json:"activity,omitempty"`
+	Billable        *bool    `json:"billable,omitempty"`
+	HourlyRate      *float64 `json:"hourly_rate,omitempty"`
+}
+
+type TimeEntryFilter struct {
+	CaseID *uuid.UUID
+	UserID *uuid.UUID
+	From   string
+	To     string
+	Limit  int
+	Offset int
+}
+
+type TimeEntrySummary struct {
+	GroupKey       string  `db:"group_key" json:"group_key"`
+	TotalMinutes   int     `db:"total_minutes" json:"total_minutes"`
+	BillableMinutes int   `db:"billable_minutes" json:"billable_minutes"`
+	TotalAmount    float64 `db:"total_amount" json:"total_amount"`
+	EntryCount     int     `db:"entry_count" json:"entry_count"`
+}
+
+const timeEntryCols = `id, tenant_id, case_id, user_id, date, duration_minutes, description,
+	activity, billable, billed, invoice_id, hourly_rate, created_at, updated_at`
+
+func (s *TimeEntryService) ListForCase(ctx context.Context, tenantID, caseID uuid.UUID) ([]models.TimeEntry, error) {
+	var entries []models.TimeEntry
+	err := s.db.SelectContext(ctx, &entries,
+		`SELECT `+timeEntryCols+` FROM time_entries
+		 WHERE tenant_id = $1 AND case_id = $2
+		 ORDER BY date DESC, created_at DESC`,
+		tenantID, caseID)
+	if err != nil {
+		return nil, fmt.Errorf("list time entries for case: %w", err)
+	}
+	return entries, nil
+}
+
+func (s *TimeEntryService) List(ctx context.Context, tenantID uuid.UUID, filter TimeEntryFilter) ([]models.TimeEntry, int, error) {
+	if filter.Limit <= 0 {
+		filter.Limit = 20
+	}
+	if filter.Limit > 100 {
+		filter.Limit = 100
+	}
+
+	where := "WHERE tenant_id = $1"
+	args := []any{tenantID}
+	argIdx := 2
+
+	if filter.CaseID != nil {
+		where += fmt.Sprintf(" AND case_id = $%d", argIdx)
+		args = append(args, *filter.CaseID)
+		argIdx++
+	}
+	if filter.UserID != nil {
+		where += fmt.Sprintf(" AND user_id = $%d", argIdx)
+		args = append(args, *filter.UserID)
+		argIdx++
+	}
+	if filter.From != "" {
+		where += fmt.Sprintf(" AND date >= $%d", argIdx)
+		args = append(args, filter.From)
+		argIdx++
+	}
+	if filter.To != "" {
+		where += fmt.Sprintf(" AND date <= $%d", argIdx)
+		args = append(args, filter.To)
+		argIdx++
+	}
+
+	var total int
+	err := s.db.GetContext(ctx, &total,
+		"SELECT COUNT(*) FROM time_entries "+where, args...)
+	if err != nil {
+		return nil, 0, fmt.Errorf("count time entries: %w", err)
+	}
+
+	query := fmt.Sprintf("SELECT %s FROM time_entries %s ORDER BY date DESC, created_at DESC LIMIT $%d OFFSET $%d",
+		timeEntryCols, where, argIdx, argIdx+1)
+	args = append(args, filter.Limit, filter.Offset)
+
+	var entries []models.TimeEntry
+	err = s.db.SelectContext(ctx, &entries, query, args...)
+	if err != nil {
+		return nil, 0, fmt.Errorf("list time entries: %w", err)
+	}
+	return entries, total, nil
+}
+
+func (s *TimeEntryService) GetByID(ctx context.Context, tenantID, entryID uuid.UUID) (*models.TimeEntry, error) {
+	var entry models.TimeEntry
+	err := s.db.GetContext(ctx, &entry,
+		`SELECT `+timeEntryCols+` FROM time_entries WHERE tenant_id = $1 AND id = $2`,
+		tenantID, entryID)
+	if err == sql.ErrNoRows {
+		return nil, nil
+	}
+	if err != nil {
+		return nil, fmt.Errorf("get time entry: %w", err)
+	}
+	return &entry, nil
+}
+
+func (s *TimeEntryService) Create(ctx context.Context, tenantID, userID uuid.UUID, input CreateTimeEntryInput) (*models.TimeEntry, error) {
+	billable := true
+	if input.Billable != nil {
+		billable = *input.Billable
+	}
+
+	// If no hourly rate provided, look up the current billing rate
+	hourlyRate := input.HourlyRate
+	if hourlyRate == nil {
+		var rate float64
+		err := s.db.GetContext(ctx, &rate,
+			`SELECT rate FROM billing_rates
+			 WHERE tenant_id = $1 AND (user_id = $2 OR user_id IS NULL)
+			 AND valid_from <= $3 AND (valid_to IS NULL OR valid_to >= $3)
+			 ORDER BY user_id NULLS LAST LIMIT 1`,
+			tenantID, userID, input.Date)
+		if err == nil {
+			hourlyRate = &rate
+		}
+	}
+
+	var entry models.TimeEntry
+	err := s.db.QueryRowxContext(ctx,
+		`INSERT INTO time_entries (tenant_id, case_id, user_id, date, duration_minutes, description, activity, billable, hourly_rate)
+		 VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9)
+		 RETURNING `+timeEntryCols,
+		tenantID, input.CaseID, userID, input.Date, input.DurationMinutes, input.Description, input.Activity, billable, hourlyRate,
+	).StructScan(&entry)
+	if err != nil {
+		return nil, fmt.Errorf("create time entry: %w", err)
+	}
+
+	s.audit.Log(ctx, "create", "time_entry", &entry.ID, nil, entry)
+	return &entry, nil
+}
+
+func (s *TimeEntryService) Update(ctx context.Context, tenantID, entryID uuid.UUID, input UpdateTimeEntryInput) (*models.TimeEntry, error) {
+	old, err := s.GetByID(ctx, tenantID, entryID)
+	if err != nil {
+		return nil, err
+	}
+	if old == nil {
+		return nil, fmt.Errorf("time entry not found")
+	}
+	if old.Billed {
+		return nil, fmt.Errorf("cannot update a billed time entry")
+	}
+
+	var entry models.TimeEntry
+	err = s.db.QueryRowxContext(ctx,
+		`UPDATE time_entries SET
+			date = COALESCE($3, date),
+			duration_minutes = COALESCE($4, duration_minutes),
+			description = COALESCE($5, description),
+			activity = COALESCE($6, activity),
+			billable = COALESCE($7, billable),
+			hourly_rate = COALESCE($8, hourly_rate),
+			updated_at = now()
+		 WHERE tenant_id = $1 AND id = $2
+		 RETURNING `+timeEntryCols,
+		tenantID, entryID, input.Date, input.DurationMinutes, input.Description, input.Activity, input.Billable, input.HourlyRate,
+	).StructScan(&entry)
+	if err != nil {
+		return nil, fmt.Errorf("update time entry: %w", err)
+	}
+
+	s.audit.Log(ctx, "update", "time_entry", &entry.ID, old, entry)
+	return &entry, nil
+}
+
+func (s *TimeEntryService) Delete(ctx context.Context, tenantID, entryID uuid.UUID) error {
+	old, err := s.GetByID(ctx, tenantID, entryID)
+	if err != nil {
+		return err
+	}
+	if old == nil {
+		return fmt.Errorf("time entry not found")
+	}
+	if old.Billed {
+		return fmt.Errorf("cannot delete a billed time entry")
+	}
+
+	_, err = s.db.ExecContext(ctx,
+		`DELETE FROM time_entries WHERE tenant_id = $1 AND id = $2`,
+		tenantID, entryID)
+	if err != nil {
+		return fmt.Errorf("delete time entry: %w", err)
+	}
+
+	s.audit.Log(ctx, "delete", "time_entry", &entryID, old, nil)
+	return nil
+}
+
+func (s *TimeEntryService) Summary(ctx context.Context, tenantID uuid.UUID, groupBy string, from, to string) ([]TimeEntrySummary, error) {
+	var groupExpr string
+	switch groupBy {
+	case "user":
+		groupExpr = "user_id::text"
+	case "month":
+		groupExpr = "to_char(date, 'YYYY-MM')"
+	default:
+		groupExpr = "case_id::text"
+	}
+
+	where := "WHERE tenant_id = $1"
+	args := []any{tenantID}
+	argIdx := 2
+
+	if from != "" {
+		where += fmt.Sprintf(" AND date >= $%d", argIdx)
+		args = append(args, from)
+		argIdx++
+	}
+	if to != "" {
+		where += fmt.Sprintf(" AND date <= $%d", argIdx)
+		args = append(args, to)
+		argIdx++
+	}
+
+	query := fmt.Sprintf(`SELECT %s AS group_key,
+		SUM(duration_minutes) AS total_minutes,
+		SUM(CASE WHEN billable THEN duration_minutes ELSE 0 END) AS billable_minutes,
+		SUM(CASE WHEN billable AND hourly_rate IS NOT NULL THEN duration_minutes * hourly_rate / 60.0 ELSE 0 END) AS total_amount,
+		COUNT(*) AS entry_count
+		FROM time_entries %s
+		GROUP BY %s
+		ORDER BY %s`,
+		groupExpr, where, groupExpr, groupExpr)
+
+	var summaries []TimeEntrySummary
+	err := s.db.SelectContext(ctx, &summaries, query, args...)
+	if err != nil {
+		return nil, fmt.Errorf("time entry summary: %w", err)
+	}
+	return summaries, nil
+}

frontend/src/app/(app)/abrechnung/page.tsx

@@ -0,0 +1,164 @@
+"use client";
+
+import { useQuery } from "@tanstack/react-query";
+import { api } from "@/lib/api";
+import type { TimeEntry } from "@/lib/types";
+import { format } from "date-fns";
+import { de } from "date-fns/locale";
+import { Timer, Loader2 } from "lucide-react";
+import { useState } from "react";
+import Link from "next/link";
+import { Breadcrumb } from "@/components/layout/Breadcrumb";
+
+function formatDuration(minutes: number): string {
+  const h = Math.floor(minutes / 60);
+  const m = minutes % 60;
+  if (h === 0) return `${m}min`;
+  if (m === 0) return `${h}h`;
+  return `${h}h ${m}min`;
+}
+
+export default function AbrechnungPage() {
+  const [from, setFrom] = useState(() => {
+    const d = new Date();
+    d.setDate(1);
+    return format(d, "yyyy-MM-dd");
+  });
+  const [to, setTo] = useState(() => format(new Date(), "yyyy-MM-dd"));
+
+  const { data, isLoading } = useQuery({
+    queryKey: ["time-entries", from, to],
+    queryFn: () =>
+      api.get<{ time_entries: TimeEntry[]; total: number }>(
+        `/time-entries?from=${from}&to=${to}&limit=100`,
+      ),
+  });
+
+  const entries = data?.time_entries ?? [];
+  const totalMinutes = entries.reduce((s, e) => s + e.duration_minutes, 0);
+  const billableMinutes = entries
+    .filter((e) => e.billable)
+    .reduce((s, e) => s + e.duration_minutes, 0);
+  const totalAmount = entries
+    .filter((e) => e.billable && e.hourly_rate)
+    .reduce((s, e) => s + (e.duration_minutes / 60) * (e.hourly_rate ?? 0), 0);
+
+  return (
+    <div className="animate-fade-in">
+      <Breadcrumb
+        items={[
+          { label: "Dashboard", href: "/dashboard" },
+          { label: "Abrechnung" },
+        ]}
+      />
+
+      <div className="mt-4 flex flex-col gap-3 sm:flex-row sm:items-center sm:justify-between">
+        <h1 className="text-lg font-semibold text-neutral-900">
+          Zeiterfassung
+        </h1>
+        <Link
+          href="/abrechnung/rechnungen"
+          className="text-sm text-neutral-500 transition-colors hover:text-neutral-700"
+        >
+          Rechnungen ansehen &rarr;
+        </Link>
+      </div>
+
+      {/* Filters */}
+      <div className="mt-4 flex flex-wrap items-center gap-3">
+        <div className="flex items-center gap-2">
+          <label className="text-xs text-neutral-500">Von</label>
+          <input
+            type="date"
+            value={from}
+            onChange={(e) => setFrom(e.target.value)}
+            className="rounded-md border border-neutral-300 px-2 py-1 text-sm focus:border-neutral-500 focus:outline-none"
+          />
+        </div>
+        <div className="flex items-center gap-2">
+          <label className="text-xs text-neutral-500">Bis</label>
+          <input
+            type="date"
+            value={to}
+            onChange={(e) => setTo(e.target.value)}
+            className="rounded-md border border-neutral-300 px-2 py-1 text-sm focus:border-neutral-500 focus:outline-none"
+          />
+        </div>
+      </div>
+
+      {/* Summary cards */}
+      <div className="mt-4 grid grid-cols-1 gap-3 sm:grid-cols-3">
+        <div className="rounded-md border border-neutral-200 bg-white p-4">
+          <p className="text-xs text-neutral-500">Gesamt</p>
+          <p className="mt-1 text-xl font-semibold text-neutral-900">
+            {formatDuration(totalMinutes)}
+          </p>
+        </div>
+        <div className="rounded-md border border-neutral-200 bg-white p-4">
+          <p className="text-xs text-neutral-500">Abrechenbar</p>
+          <p className="mt-1 text-xl font-semibold text-neutral-900">
+            {formatDuration(billableMinutes)}
+          </p>
+        </div>
+        <div className="rounded-md border border-neutral-200 bg-white p-4">
+          <p className="text-xs text-neutral-500">Betrag</p>
+          <p className="mt-1 text-xl font-semibold text-neutral-900">
+            {totalAmount.toFixed(2)} EUR
+          </p>
+        </div>
+      </div>
+
+      {/* Entries */}
+      {isLoading ? (
+        <div className="flex items-center justify-center py-8">
+          <Loader2 className="h-5 w-5 animate-spin text-neutral-400" />
+        </div>
+      ) : entries.length === 0 ? (
+        <div className="flex flex-col items-center py-12 text-center">
+          <div className="rounded-xl bg-neutral-100 p-3">
+            <Timer className="h-5 w-5 text-neutral-400" />
+          </div>
+          <p className="mt-2 text-sm text-neutral-500">
+            Keine Zeiteintraege im gewaehlten Zeitraum.
+          </p>
+        </div>
+      ) : (
+        <div className="mt-4 space-y-2">
+          {entries.map((entry) => (
+            <div
+              key={entry.id}
+              className="flex items-center justify-between rounded-md border border-neutral-200 bg-white px-4 py-3"
+            >
+              <div className="min-w-0 flex-1">
+                <p className="text-sm font-medium text-neutral-900 truncate">
+                  {entry.description}
+                </p>
+                <div className="mt-0.5 flex gap-3 text-xs text-neutral-500">
+                  <span>
+                    {format(new Date(entry.date), "d. MMM yyyy", { locale: de })}
+                  </span>
+                  <Link
+                    href={`/cases/${entry.case_id}/zeiterfassung`}
+                    className="hover:text-neutral-700"
+                  >
+                    Akte ansehen
+                  </Link>
+                </div>
+              </div>
+              <div className="flex items-center gap-4 ml-4 text-sm">
+                {entry.billable ? (
+                  <span className="text-emerald-600">abrechenbar</span>
+                ) : (
+                  <span className="text-neutral-400">intern</span>
+                )}
+                <span className="font-medium text-neutral-900 whitespace-nowrap">
+                  {formatDuration(entry.duration_minutes)}
+                </span>
+              </div>
+            </div>
+          ))}
+        </div>
+      )}
+    </div>
+  );
+}

frontend/src/app/(app)/abrechnung/rechnungen/[id]/page.tsx

@@ -0,0 +1,225 @@
+"use client";
+
+import { useQuery, useMutation, useQueryClient } from "@tanstack/react-query";
+import { useParams } from "next/navigation";
+import { api } from "@/lib/api";
+import type { Invoice } from "@/lib/types";
+import { format } from "date-fns";
+import { de } from "date-fns/locale";
+import { Loader2, AlertTriangle } from "lucide-react";
+import { Breadcrumb } from "@/components/layout/Breadcrumb";
+
+const STATUS_BADGE: Record<string, string> = {
+  draft: "bg-neutral-100 text-neutral-600",
+  sent: "bg-blue-50 text-blue-700",
+  paid: "bg-emerald-50 text-emerald-700",
+  cancelled: "bg-red-50 text-red-600",
+};
+
+const STATUS_LABEL: Record<string, string> = {
+  draft: "Entwurf",
+  sent: "Versendet",
+  paid: "Bezahlt",
+  cancelled: "Storniert",
+};
+
+const TRANSITIONS: Record<string, { label: string; next: string }[]> = {
+  draft: [
+    { label: "Als versendet markieren", next: "sent" },
+    { label: "Stornieren", next: "cancelled" },
+  ],
+  sent: [
+    { label: "Als bezahlt markieren", next: "paid" },
+    { label: "Stornieren", next: "cancelled" },
+  ],
+  paid: [],
+  cancelled: [],
+};
+
+export default function InvoiceDetailPage() {
+  const { id } = useParams<{ id: string }>();
+  const queryClient = useQueryClient();
+
+  const { data: invoice, isLoading, error } = useQuery({
+    queryKey: ["invoice", id],
+    queryFn: () => api.get<Invoice>(`/invoices/${id}`),
+  });
+
+  const statusMutation = useMutation({
+    mutationFn: (status: string) =>
+      api.patch<Invoice>(`/invoices/${id}/status`, { status }),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ["invoice", id] });
+      queryClient.invalidateQueries({ queryKey: ["invoices"] });
+    },
+  });
+
+  if (isLoading) {
+    return (
+      <div className="flex items-center justify-center py-12">
+        <Loader2 className="h-5 w-5 animate-spin text-neutral-400" />
+      </div>
+    );
+  }
+
+  if (error || !invoice) {
+    return (
+      <div className="py-12 text-center">
+        <AlertTriangle className="mx-auto h-6 w-6 text-red-500" />
+        <p className="mt-2 text-sm text-neutral-500">
+          Rechnung nicht gefunden.
+        </p>
+      </div>
+    );
+  }
+
+  const items = Array.isArray(invoice.items) ? invoice.items : [];
+  const actions = TRANSITIONS[invoice.status] ?? [];
+
+  return (
+    <div className="animate-fade-in">
+      <Breadcrumb
+        items={[
+          { label: "Dashboard", href: "/dashboard" },
+          { label: "Abrechnung", href: "/abrechnung" },
+          { label: "Rechnungen", href: "/abrechnung/rechnungen" },
+          { label: invoice.invoice_number },
+        ]}
+      />
+
+      <div className="mt-4 flex flex-col gap-3 sm:flex-row sm:items-start sm:justify-between">
+        <div>
+          <div className="flex items-center gap-3">
+            <h1 className="text-lg font-semibold text-neutral-900">
+              {invoice.invoice_number}
+            </h1>
+            <span
+              className={`rounded-full px-2 py-0.5 text-xs font-medium ${STATUS_BADGE[invoice.status]}`}
+            >
+              {STATUS_LABEL[invoice.status]}
+            </span>
+          </div>
+          <p className="mt-1 text-sm text-neutral-500">
+            {invoice.client_name}
+          </p>
+        </div>
+        <div className="flex gap-2">
+          {actions.map((action) => (
+            <button
+              key={action.next}
+              onClick={() => statusMutation.mutate(action.next)}
+              disabled={statusMutation.isPending}
+              className="rounded-md bg-neutral-900 px-3 py-1.5 text-sm font-medium text-white transition-colors hover:bg-neutral-800 disabled:opacity-50"
+            >
+              {action.label}
+            </button>
+          ))}
+        </div>
+      </div>
+
+      {/* Invoice details */}
+      <div className="mt-6 rounded-md border border-neutral-200 bg-white">
+        {/* Client info */}
+        <div className="border-b border-neutral-100 p-4">
+          <p className="text-xs text-neutral-500">Empfaenger</p>
+          <p className="mt-1 text-sm font-medium text-neutral-900">
+            {invoice.client_name}
+          </p>
+          {invoice.client_address && (
+            <p className="mt-0.5 text-sm text-neutral-500 whitespace-pre-line">
+              {invoice.client_address}
+            </p>
+          )}
+        </div>
+
+        {/* Dates */}
+        <div className="flex flex-wrap gap-6 border-b border-neutral-100 p-4">
+          {invoice.issued_at && (
+            <div>
+              <p className="text-xs text-neutral-500">Rechnungsdatum</p>
+              <p className="mt-0.5 text-sm text-neutral-900">
+                {format(new Date(invoice.issued_at), "d. MMMM yyyy", { locale: de })}
+              </p>
+            </div>
+          )}
+          {invoice.due_at && (
+            <div>
+              <p className="text-xs text-neutral-500">Faellig am</p>
+              <p className="mt-0.5 text-sm text-neutral-900">
+                {format(new Date(invoice.due_at), "d. MMMM yyyy", { locale: de })}
+              </p>
+            </div>
+          )}
+          {invoice.paid_at && (
+            <div>
+              <p className="text-xs text-neutral-500">Bezahlt am</p>
+              <p className="mt-0.5 text-sm text-neutral-900">
+                {format(new Date(invoice.paid_at), "d. MMMM yyyy", { locale: de })}
+              </p>
+            </div>
+          )}
+        </div>
+
+        {/* Line items */}
+        <div className="p-4">
+          <table className="w-full text-sm">
+            <thead>
+              <tr className="border-b border-neutral-100 text-left text-xs text-neutral-500">
+                <th className="pb-2 font-medium">Beschreibung</th>
+                <th className="pb-2 font-medium text-right">Betrag</th>
+              </tr>
+            </thead>
+            <tbody>
+              {items.map((item, i) => (
+                <tr key={i} className="border-b border-neutral-50">
+                  <td className="py-2 text-neutral-900">
+                    {item.description}
+                    {item.duration_minutes && item.hourly_rate && (
+                      <span className="ml-2 text-xs text-neutral-400">
+                        ({Math.floor(item.duration_minutes / 60)}h{" "}
+                        {item.duration_minutes % 60}min x {item.hourly_rate} EUR/h)
+                      </span>
+                    )}
+                  </td>
+                  <td className="py-2 text-right text-neutral-900">
+                    {item.amount.toFixed(2)} EUR
+                  </td>
+                </tr>
+              ))}
+            </tbody>
+          </table>
+        </div>
+
+        {/* Totals */}
+        <div className="border-t border-neutral-200 p-4">
+          <div className="flex justify-end">
+            <div className="w-48 space-y-1">
+              <div className="flex justify-between text-sm">
+                <span className="text-neutral-500">Netto</span>
+                <span>{invoice.subtotal.toFixed(2)} EUR</span>
+              </div>
+              <div className="flex justify-between text-sm">
+                <span className="text-neutral-500">
+                  USt. {invoice.tax_rate}%
+                </span>
+                <span>{invoice.tax_amount.toFixed(2)} EUR</span>
+              </div>
+              <div className="flex justify-between border-t border-neutral-200 pt-1 text-sm font-semibold">
+                <span>Gesamt</span>
+                <span>{invoice.total.toFixed(2)} EUR</span>
+              </div>
+            </div>
+          </div>
+        </div>
+
+        {/* Notes */}
+        {invoice.notes && (
+          <div className="border-t border-neutral-100 p-4">
+            <p className="text-xs text-neutral-500">Anmerkungen</p>
+            <p className="mt-1 text-sm text-neutral-700">{invoice.notes}</p>
+          </div>
+        )}
+      </div>
+    </div>
+  );
+}

frontend/src/app/(app)/abrechnung/rechnungen/page.tsx

@@ -0,0 +1,118 @@
+"use client";
+
+import { useQuery } from "@tanstack/react-query";
+import { api } from "@/lib/api";
+import type { Invoice } from "@/lib/types";
+import { format } from "date-fns";
+import { de } from "date-fns/locale";
+import { Receipt, Loader2 } from "lucide-react";
+import Link from "next/link";
+import { useState } from "react";
+import { Breadcrumb } from "@/components/layout/Breadcrumb";
+
+const STATUS_BADGE: Record<string, string> = {
+  draft: "bg-neutral-100 text-neutral-600",
+  sent: "bg-blue-50 text-blue-700",
+  paid: "bg-emerald-50 text-emerald-700",
+  cancelled: "bg-red-50 text-red-600",
+};
+
+const STATUS_LABEL: Record<string, string> = {
+  draft: "Entwurf",
+  sent: "Versendet",
+  paid: "Bezahlt",
+  cancelled: "Storniert",
+};
+
+export default function RechnungenPage() {
+  const [statusFilter, setStatusFilter] = useState("");
+
+  const { data, isLoading } = useQuery({
+    queryKey: ["invoices", statusFilter],
+    queryFn: () => {
+      const params = statusFilter ? `?status=${statusFilter}` : "";
+      return api.get<{ invoices: Invoice[] }>(`/invoices${params}`);
+    },
+  });
+
+  const invoices = data?.invoices ?? [];
+
+  return (
+    <div className="animate-fade-in">
+      <Breadcrumb
+        items={[
+          { label: "Dashboard", href: "/dashboard" },
+          { label: "Abrechnung", href: "/abrechnung" },
+          { label: "Rechnungen" },
+        ]}
+      />
+
+      <div className="mt-4 flex items-center justify-between">
+        <h1 className="text-lg font-semibold text-neutral-900">Rechnungen</h1>
+      </div>
+
+      {/* Filters */}
+      <div className="mt-4 flex gap-2">
+        {["", "draft", "sent", "paid", "cancelled"].map((s) => (
+          <button
+            key={s}
+            onClick={() => setStatusFilter(s)}
+            className={`rounded-md px-2.5 py-1 text-xs font-medium transition-colors ${
+              statusFilter === s
+                ? "bg-neutral-900 text-white"
+                : "bg-neutral-100 text-neutral-600 hover:bg-neutral-200"
+            }`}
+          >
+            {s === "" ? "Alle" : STATUS_LABEL[s]}
+          </button>
+        ))}
+      </div>
+
+      {isLoading ? (
+        <div className="flex items-center justify-center py-8">
+          <Loader2 className="h-5 w-5 animate-spin text-neutral-400" />
+        </div>
+      ) : invoices.length === 0 ? (
+        <div className="flex flex-col items-center py-12 text-center">
+          <div className="rounded-xl bg-neutral-100 p-3">
+            <Receipt className="h-5 w-5 text-neutral-400" />
+          </div>
+          <p className="mt-2 text-sm text-neutral-500">
+            Keine Rechnungen vorhanden.
+          </p>
+        </div>
+      ) : (
+        <div className="mt-4 space-y-2">
+          {invoices.map((inv) => (
+            <Link
+              key={inv.id}
+              href={`/abrechnung/rechnungen/${inv.id}`}
+              className="flex items-center justify-between rounded-md border border-neutral-200 bg-white px-4 py-3 transition-colors hover:bg-neutral-50"
+            >
+              <div>
+                <div className="flex items-center gap-2">
+                  <p className="text-sm font-medium text-neutral-900">
+                    {inv.invoice_number}
+                  </p>
+                  <span
+                    className={`rounded-full px-2 py-0.5 text-xs font-medium ${STATUS_BADGE[inv.status]}`}
+                  >
+                    {STATUS_LABEL[inv.status]}
+                  </span>
+                </div>
+                <p className="mt-0.5 text-xs text-neutral-500">
+                  {inv.client_name}
+                  {inv.issued_at &&
+                    ` — ${format(new Date(inv.issued_at), "d. MMM yyyy", { locale: de })}`}
+                </p>
+              </div>
+              <p className="text-sm font-semibold text-neutral-900">
+                {inv.total.toFixed(2)} EUR
+              </p>
+            </Link>
+          ))}
+        </div>
+      )}
+    </div>
+  );
+}

frontend/src/app/(app)/cases/[id]/layout.tsx

@@ -17,6 +17,7 @@ import {
   StickyNote,
   AlertTriangle,
   ScrollText,
+  Timer,
 } from "lucide-react";
 import { format } from "date-fns";
 import { de } from "date-fns/locale";
@@ -46,6 +47,7 @@ const TABS = [
   { segment: "dokumente", label: "Dokumente", icon: FileText },
   { segment: "parteien", label: "Parteien", icon: Users },
   { segment: "mitarbeiter", label: "Mitarbeiter", icon: UserCheck },
+  { segment: "zeiterfassung", label: "Zeiterfassung", icon: Timer },
   { segment: "notizen", label: "Notizen", icon: StickyNote },
   { segment: "protokoll", label: "Protokoll", icon: ScrollText },
 ] as const;
@@ -56,6 +58,7 @@ const TAB_LABELS: Record<string, string> = {
   dokumente: "Dokumente",
   parteien: "Parteien",
   mitarbeiter: "Mitarbeiter",
+  zeiterfassung: "Zeiterfassung",
   notizen: "Notizen",
   protokoll: "Protokoll",
 };

frontend/src/app/(app)/cases/[id]/zeiterfassung/page.tsx

@@ -0,0 +1,306 @@
+"use client";
+
+import { useQuery, useMutation, useQueryClient } from "@tanstack/react-query";
+import { useParams } from "next/navigation";
+import { api } from "@/lib/api";
+import type { TimeEntry } from "@/lib/types";
+import { format } from "date-fns";
+import { de } from "date-fns/locale";
+import { Timer, Loader2, Plus, Trash2 } from "lucide-react";
+import { useState } from "react";
+
+function formatDuration(minutes: number): string {
+  const h = Math.floor(minutes / 60);
+  const m = minutes % 60;
+  if (h === 0) return `${m}min`;
+  if (m === 0) return `${h}h`;
+  return `${h}h ${m}min`;
+}
+
+function formatAmount(minutes: number, rate?: number): string {
+  if (!rate) return "-";
+  return `${((minutes / 60) * rate).toFixed(2)} EUR`;
+}
+
+const ACTIVITIES = [
+  { value: "", label: "Keine Kategorie" },
+  { value: "research", label: "Recherche" },
+  { value: "drafting", label: "Entwurf" },
+  { value: "hearing", label: "Verhandlung" },
+  { value: "call", label: "Telefonat" },
+  { value: "review", label: "Prüfung" },
+  { value: "travel", label: "Reise" },
+  { value: "meeting", label: "Besprechung" },
+];
+
+export default function ZeiterfassungPage() {
+  const { id } = useParams<{ id: string }>();
+  const queryClient = useQueryClient();
+  const [showForm, setShowForm] = useState(false);
+  const [desc, setDesc] = useState("");
+  const [hours, setHours] = useState("");
+  const [minutes, setMinutes] = useState("");
+  const [date, setDate] = useState(format(new Date(), "yyyy-MM-dd"));
+  const [activity, setActivity] = useState("");
+  const [billable, setBillable] = useState(true);
+
+  const { data, isLoading } = useQuery({
+    queryKey: ["case-time-entries", id],
+    queryFn: () =>
+      api.get<{ time_entries: TimeEntry[] }>(`/cases/${id}/time-entries`),
+  });
+
+  const createMutation = useMutation({
+    mutationFn: (input: {
+      description: string;
+      duration_minutes: number;
+      date: string;
+      activity?: string;
+      billable: boolean;
+    }) => api.post<TimeEntry>(`/cases/${id}/time-entries`, input),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ["case-time-entries", id] });
+      setShowForm(false);
+      setDesc("");
+      setHours("");
+      setMinutes("");
+      setActivity("");
+      setBillable(true);
+    },
+  });
+
+  const deleteMutation = useMutation({
+    mutationFn: (entryId: string) =>
+      api.delete(`/time-entries/${entryId}`),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ["case-time-entries", id] });
+    },
+  });
+
+  function handleSubmit(e: React.FormEvent) {
+    e.preventDefault();
+    const totalMinutes = (parseInt(hours || "0") * 60) + parseInt(minutes || "0");
+    if (totalMinutes <= 0 || !desc.trim()) return;
+    createMutation.mutate({
+      description: desc.trim(),
+      duration_minutes: totalMinutes,
+      date,
+      activity: activity || undefined,
+      billable,
+    });
+  }
+
+  if (isLoading) {
+    return (
+      <div className="flex items-center justify-center py-8">
+        <Loader2 className="h-5 w-5 animate-spin text-neutral-400" />
+      </div>
+    );
+  }
+
+  const entries = data?.time_entries ?? [];
+  const totalMinutes = entries.reduce((s, e) => s + e.duration_minutes, 0);
+  const billableMinutes = entries
+    .filter((e) => e.billable)
+    .reduce((s, e) => s + e.duration_minutes, 0);
+
+  return (
+    <div className="space-y-4">
+      {/* Summary bar */}
+      <div className="flex flex-wrap items-center justify-between gap-3">
+        <div className="flex gap-6 text-sm text-neutral-500">
+          <span>
+            Gesamt: <span className="font-medium text-neutral-900">{formatDuration(totalMinutes)}</span>
+          </span>
+          <span>
+            Abrechenbar: <span className="font-medium text-neutral-900">{formatDuration(billableMinutes)}</span>
+          </span>
+        </div>
+        <button
+          onClick={() => setShowForm(!showForm)}
+          className="inline-flex items-center gap-1.5 rounded-md bg-neutral-900 px-3 py-1.5 text-sm font-medium text-white transition-colors hover:bg-neutral-800"
+        >
+          <Plus className="h-3.5 w-3.5" />
+          Eintrag
+        </button>
+      </div>
+
+      {/* Quick add form */}
+      {showForm && (
+        <form
+          onSubmit={handleSubmit}
+          className="rounded-md border border-neutral-200 bg-neutral-50 p-4 space-y-3"
+        >
+          <div>
+            <label className="block text-xs font-medium text-neutral-600 mb-1">
+              Beschreibung
+            </label>
+            <input
+              type="text"
+              value={desc}
+              onChange={(e) => setDesc(e.target.value)}
+              placeholder="Was wurde getan?"
+              className="w-full rounded-md border border-neutral-300 px-3 py-1.5 text-sm focus:border-neutral-500 focus:outline-none"
+              required
+            />
+          </div>
+          <div className="flex flex-wrap gap-3">
+            <div className="flex-1 min-w-[120px]">
+              <label className="block text-xs font-medium text-neutral-600 mb-1">
+                Dauer
+              </label>
+              <div className="flex gap-2">
+                <div className="flex items-center gap-1">
+                  <input
+                    type="number"
+                    min="0"
+                    value={hours}
+                    onChange={(e) => setHours(e.target.value)}
+                    placeholder="0"
+                    className="w-16 rounded-md border border-neutral-300 px-2 py-1.5 text-sm focus:border-neutral-500 focus:outline-none"
+                  />
+                  <span className="text-xs text-neutral-500">h</span>
+                </div>
+                <div className="flex items-center gap-1">
+                  <input
+                    type="number"
+                    min="0"
+                    max="59"
+                    value={minutes}
+                    onChange={(e) => setMinutes(e.target.value)}
+                    placeholder="0"
+                    className="w-16 rounded-md border border-neutral-300 px-2 py-1.5 text-sm focus:border-neutral-500 focus:outline-none"
+                  />
+                  <span className="text-xs text-neutral-500">min</span>
+                </div>
+              </div>
+            </div>
+            <div className="flex-1 min-w-[120px]">
+              <label className="block text-xs font-medium text-neutral-600 mb-1">
+                Datum
+              </label>
+              <input
+                type="date"
+                value={date}
+                onChange={(e) => setDate(e.target.value)}
+                className="w-full rounded-md border border-neutral-300 px-3 py-1.5 text-sm focus:border-neutral-500 focus:outline-none"
+              />
+            </div>
+            <div className="flex-1 min-w-[120px]">
+              <label className="block text-xs font-medium text-neutral-600 mb-1">
+                Kategorie
+              </label>
+              <select
+                value={activity}
+                onChange={(e) => setActivity(e.target.value)}
+                className="w-full rounded-md border border-neutral-300 px-3 py-1.5 text-sm focus:border-neutral-500 focus:outline-none"
+              >
+                {ACTIVITIES.map((a) => (
+                  <option key={a.value} value={a.value}>
+                    {a.label}
+                  </option>
+                ))}
+              </select>
+            </div>
+          </div>
+          <div className="flex items-center justify-between">
+            <label className="flex items-center gap-2 text-sm text-neutral-600">
+              <input
+                type="checkbox"
+                checked={billable}
+                onChange={(e) => setBillable(e.target.checked)}
+                className="rounded border-neutral-300"
+              />
+              Abrechenbar
+            </label>
+            <div className="flex gap-2">
+              <button
+                type="button"
+                onClick={() => setShowForm(false)}
+                className="rounded-md px-3 py-1.5 text-sm text-neutral-600 transition-colors hover:bg-neutral-100"
+              >
+                Abbrechen
+              </button>
+              <button
+                type="submit"
+                disabled={createMutation.isPending}
+                className="rounded-md bg-neutral-900 px-3 py-1.5 text-sm font-medium text-white transition-colors hover:bg-neutral-800 disabled:opacity-50"
+              >
+                {createMutation.isPending ? "Speichern..." : "Speichern"}
+              </button>
+            </div>
+          </div>
+          {createMutation.isError && (
+            <p className="text-sm text-red-600">Fehler beim Speichern.</p>
+          )}
+        </form>
+      )}
+
+      {/* Entries list */}
+      {entries.length === 0 ? (
+        <div className="flex flex-col items-center py-8 text-center">
+          <div className="rounded-xl bg-neutral-100 p-3">
+            <Timer className="h-5 w-5 text-neutral-400" />
+          </div>
+          <p className="mt-2 text-sm text-neutral-500">
+            Keine Zeiteintraege vorhanden.
+          </p>
+        </div>
+      ) : (
+        <div className="space-y-2">
+          {entries.map((entry) => (
+            <div
+              key={entry.id}
+              className="flex items-center justify-between rounded-md border border-neutral-200 bg-white px-4 py-3"
+            >
+              <div className="min-w-0 flex-1">
+                <div className="flex items-center gap-2">
+                  <p className="text-sm font-medium text-neutral-900 truncate">
+                    {entry.description}
+                  </p>
+                  {entry.activity && (
+                    <span className="shrink-0 rounded-full bg-neutral-100 px-2 py-0.5 text-xs text-neutral-500">
+                      {ACTIVITIES.find((a) => a.value === entry.activity)?.label ?? entry.activity}
+                    </span>
+                  )}
+                  {!entry.billable && (
+                    <span className="shrink-0 rounded-full bg-neutral-100 px-2 py-0.5 text-xs text-neutral-400">
+                      nicht abrechenbar
+                    </span>
+                  )}
+                  {entry.billed && (
+                    <span className="shrink-0 rounded-full bg-emerald-50 px-2 py-0.5 text-xs text-emerald-700">
+                      abgerechnet
+                    </span>
+                  )}
+                </div>
+                <div className="mt-0.5 flex gap-4 text-xs text-neutral-500">
+                  <span>
+                    {format(new Date(entry.date), "d. MMM yyyy", { locale: de })}
+                  </span>
+                  {entry.hourly_rate && (
+                    <span>{formatAmount(entry.duration_minutes, entry.hourly_rate)}</span>
+                  )}
+                </div>
+              </div>
+              <div className="flex items-center gap-3 ml-4">
+                <span className="text-sm font-medium text-neutral-900 whitespace-nowrap">
+                  {formatDuration(entry.duration_minutes)}
+                </span>
+                {!entry.billed && (
+                  <button
+                    onClick={() => deleteMutation.mutate(entry.id)}
+                    className="rounded-md p-1 text-neutral-400 transition-colors hover:bg-red-50 hover:text-red-600"
+                    title="Loeschen"
+                  >
+                    <Trash2 className="h-3.5 w-3.5" />
+                  </button>
+                )}
+              </div>
+            </div>
+          ))}
+        </div>
+      )}
+    </div>
+  );
+}

frontend/src/app/(app)/einstellungen/abrechnung/page.tsx

@@ -0,0 +1,166 @@
+"use client";
+
+import { useQuery, useMutation, useQueryClient } from "@tanstack/react-query";
+import { api } from "@/lib/api";
+import type { BillingRate } from "@/lib/types";
+import { format } from "date-fns";
+import { de } from "date-fns/locale";
+import { Loader2, Plus } from "lucide-react";
+import { useState } from "react";
+import { Breadcrumb } from "@/components/layout/Breadcrumb";
+
+export default function BillingRatesPage() {
+  const queryClient = useQueryClient();
+  const [showForm, setShowForm] = useState(false);
+  const [rate, setRate] = useState("");
+  const [validFrom, setValidFrom] = useState(format(new Date(), "yyyy-MM-dd"));
+
+  const { data, isLoading } = useQuery({
+    queryKey: ["billing-rates"],
+    queryFn: () =>
+      api.get<{ billing_rates: BillingRate[] }>("/billing-rates"),
+  });
+
+  const upsertMutation = useMutation({
+    mutationFn: (input: { rate: number; valid_from: string; currency: string }) =>
+      api.put<BillingRate>("/billing-rates", input),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ["billing-rates"] });
+      setShowForm(false);
+      setRate("");
+    },
+  });
+
+  function handleSubmit(e: React.FormEvent) {
+    e.preventDefault();
+    const rateNum = parseFloat(rate);
+    if (isNaN(rateNum) || rateNum < 0) return;
+    upsertMutation.mutate({
+      rate: rateNum,
+      valid_from: validFrom,
+      currency: "EUR",
+    });
+  }
+
+  const rates = data?.billing_rates ?? [];
+
+  return (
+    <div className="animate-fade-in">
+      <Breadcrumb
+        items={[
+          { label: "Dashboard", href: "/dashboard" },
+          { label: "Einstellungen", href: "/einstellungen" },
+          { label: "Stundensaetze" },
+        ]}
+      />
+
+      <div className="mt-4 flex items-center justify-between">
+        <h1 className="text-lg font-semibold text-neutral-900">
+          Stundensaetze
+        </h1>
+        <button
+          onClick={() => setShowForm(!showForm)}
+          className="inline-flex items-center gap-1.5 rounded-md bg-neutral-900 px-3 py-1.5 text-sm font-medium text-white transition-colors hover:bg-neutral-800"
+        >
+          <Plus className="h-3.5 w-3.5" />
+          Neuer Satz
+        </button>
+      </div>
+
+      {showForm && (
+        <form
+          onSubmit={handleSubmit}
+          className="mt-4 rounded-md border border-neutral-200 bg-neutral-50 p-4 space-y-3"
+        >
+          <div className="flex flex-wrap gap-3">
+            <div className="flex-1 min-w-[150px]">
+              <label className="block text-xs font-medium text-neutral-600 mb-1">
+                Stundensatz (EUR)
+              </label>
+              <input
+                type="number"
+                min="0"
+                step="0.01"
+                value={rate}
+                onChange={(e) => setRate(e.target.value)}
+                placeholder="z.B. 350.00"
+                className="w-full rounded-md border border-neutral-300 px-3 py-1.5 text-sm focus:border-neutral-500 focus:outline-none"
+                required
+              />
+            </div>
+            <div className="flex-1 min-w-[150px]">
+              <label className="block text-xs font-medium text-neutral-600 mb-1">
+                Gueltig ab
+              </label>
+              <input
+                type="date"
+                value={validFrom}
+                onChange={(e) => setValidFrom(e.target.value)}
+                className="w-full rounded-md border border-neutral-300 px-3 py-1.5 text-sm focus:border-neutral-500 focus:outline-none"
+                required
+              />
+            </div>
+          </div>
+          <div className="flex justify-end gap-2">
+            <button
+              type="button"
+              onClick={() => setShowForm(false)}
+              className="rounded-md px-3 py-1.5 text-sm text-neutral-600 hover:bg-neutral-100"
+            >
+              Abbrechen
+            </button>
+            <button
+              type="submit"
+              disabled={upsertMutation.isPending}
+              className="rounded-md bg-neutral-900 px-3 py-1.5 text-sm font-medium text-white hover:bg-neutral-800 disabled:opacity-50"
+            >
+              Speichern
+            </button>
+          </div>
+        </form>
+      )}
+
+      {isLoading ? (
+        <div className="flex items-center justify-center py-8">
+          <Loader2 className="h-5 w-5 animate-spin text-neutral-400" />
+        </div>
+      ) : rates.length === 0 ? (
+        <div className="mt-8 text-center">
+          <p className="text-sm text-neutral-500">
+            Noch keine Stundensaetze definiert.
+          </p>
+        </div>
+      ) : (
+        <div className="mt-4 space-y-2">
+          {rates.map((r) => (
+            <div
+              key={r.id}
+              className="flex items-center justify-between rounded-md border border-neutral-200 bg-white px-4 py-3"
+            >
+              <div>
+                <p className="text-sm font-medium text-neutral-900">
+                  {r.rate.toFixed(2)} {r.currency}/h
+                </p>
+                <p className="mt-0.5 text-xs text-neutral-500">
+                  {r.user_id ? `Benutzer: ${r.user_id.slice(0, 8)}...` : "Standard (alle Benutzer)"}
+                </p>
+              </div>
+              <div className="text-right text-xs text-neutral-500">
+                <p>
+                  Ab{" "}
+                  {format(new Date(r.valid_from), "d. MMM yyyy", { locale: de })}
+                </p>
+                {r.valid_to && (
+                  <p>
+                    Bis{" "}
+                    {format(new Date(r.valid_to), "d. MMM yyyy", { locale: de })}
+                  </p>
+                )}
+              </div>
+            </div>
+          ))}
+        </div>
+      )}
+    </div>
+  );
+}

frontend/src/components/layout/Sidebar.tsx

@@ -11,6 +11,7 @@ import {
   Settings,
   Menu,
   X,
+  Receipt,
 } from "lucide-react";
 import { useState, useEffect } from "react";
 import { usePermissions } from "@/lib/hooks/usePermissions";
@@ -27,6 +28,7 @@ const allNavigation: NavItem[] = [
   { name: "Akten", href: "/cases", icon: FolderOpen },
   { name: "Fristen", href: "/fristen", icon: Clock },
   { name: "Termine", href: "/termine", icon: Calendar },
+  { name: "Abrechnung", href: "/abrechnung", icon: Receipt, permission: "manage_billing" },
   { name: "AI Analyse", href: "/ai/extract", icon: Brain, permission: "ai_extraction" },
   { name: "Einstellungen", href: "/einstellungen", icon: Settings, permission: "manage_settings" },
 ];

frontend/src/lib/types.ts

@@ -223,6 +223,125 @@ export const CASE_ASSIGNMENT_ROLE_LABELS: Record<CaseAssignmentRole, string> = {
   viewer: "Einsicht",
 };
 
+// Time tracking & billing
+
+export interface TimeEntry {
+  id: string;
+  tenant_id: string;
+  case_id: string;
+  user_id: string;
+  date: string;
+  duration_minutes: number;
+  description: string;
+  activity?: string;
+  billable: boolean;
+  billed: boolean;
+  invoice_id?: string;
+  hourly_rate?: number;
+  created_at: string;
+  updated_at: string;
+}
+
+export interface BillingRate {
+  id: string;
+  tenant_id: string;
+  user_id?: string;
+  rate: number;
+  currency: string;
+  valid_from: string;
+  valid_to?: string;
+  created_at: string;
+}
+
+export interface InvoiceItem {
+  description: string;
+  duration_minutes?: number;
+  hourly_rate?: number;
+  amount: number;
+  time_entry_id?: string;
+}
+
+export interface Invoice {
+  id: string;
+  tenant_id: string;
+  case_id: string;
+  invoice_number: string;
+  client_name: string;
+  client_address?: string;
+  items: InvoiceItem[];
+  subtotal: number;
+  tax_rate: number;
+  tax_amount: number;
+  total: number;
+  status: "draft" | "sent" | "paid" | "cancelled";
+  issued_at?: string;
+  due_at?: string;
+  paid_at?: string;
+  notes?: string;
+  created_by: string;
+  created_at: string;
+  updated_at: string;
+}
+
+export interface TimeEntrySummary {
+  group_key: string;
+  total_minutes: number;
+  billable_minutes: number;
+  total_amount: number;
+  entry_count: number;
+}
+
+// Notifications
+export interface Notification {
+  id: string;
+  tenant_id: string;
+  user_id: string;
+  type: string;
+  title: string;
+  body?: string;
+  entity_type?: string;
+  entity_id?: string;
+  sent_at?: string;
+  read_at?: string;
+  created_at: string;
+}
+
+export interface NotificationPreferences {
+  user_id: string;
+  tenant_id: string;
+  deadline_reminder_days: number[];
+  email_enabled: boolean;
+  daily_digest: boolean;
+  created_at: string;
+  updated_at: string;
+}
+
+export interface NotificationListResponse {
+  notifications: Notification[];
+  data: Notification[];
+  total: number;
+}
+
+// Audit log
+export interface AuditLogEntry {
+  id: number;
+  tenant_id: string;
+  user_id?: string;
+  action: string;
+  entity_type: string;
+  entity_id?: string;
+  old_values?: Record<string, unknown>;
+  new_values?: Record<string, unknown>;
+  ip_address?: string;
+  user_agent?: string;
+  created_at: string;
+}
+
+export interface AuditLogResponse {
+  entries: AuditLogEntry[];
+  total: number;
+}
+
 export interface ApiError {
   error: string;
   status: number;