feat: Phase A backend — notes CRUD, detail endpoints, dashboard fix

- Create kanzlai.notes table (polymorphic FK with CHECK constraint,
  partial indexes, RLS)
- Add Note model, NoteService (ListByParent, Create, Update, Delete),
  and NoteHandler with endpoints: GET/POST /api/notes, PUT/DELETE /api/notes/{id}
- Add GET /api/deadlines/{deadlineID} detail endpoint
- Add GET /api/appointments/{id} detail endpoint
- Add GET /api/case-events/{id} detail endpoint (new CaseEventHandler)
- Fix dashboard query: add case_id to upcoming_deadlines SELECT,
  add id and case_id to recent_activity SELECT
- Register all new routes in router.go

backend/internal/handlers/appointments.go

@@ -22,6 +22,33 @@ func NewAppointmentHandler(svc *services.AppointmentService) *AppointmentHandler
 	return &AppointmentHandler{svc: svc}
 }
 
+// Get handles GET /api/appointments/{id}
+func (h *AppointmentHandler) Get(w http.ResponseWriter, r *http.Request) {
+	tenantID, ok := auth.TenantFromContext(r.Context())
+	if !ok {
+		writeError(w, http.StatusUnauthorized, "missing tenant")
+		return
+	}
+
+	id, err := uuid.Parse(r.PathValue("id"))
+	if err != nil {
+		writeError(w, http.StatusBadRequest, "invalid appointment id")
+		return
+	}
+
+	appt, err := h.svc.GetByID(r.Context(), tenantID, id)
+	if err != nil {
+		if errors.Is(err, sql.ErrNoRows) {
+			writeError(w, http.StatusNotFound, "appointment not found")
+			return
+		}
+		writeError(w, http.StatusInternalServerError, "failed to fetch appointment")
+		return
+	}
+
+	writeJSON(w, http.StatusOK, appt)
+}
+
 func (h *AppointmentHandler) List(w http.ResponseWriter, r *http.Request) {
 	tenantID, ok := auth.TenantFromContext(r.Context())
 	if !ok {

backend/internal/handlers/case_events.go

@@ -0,0 +1,52 @@
+package handlers
+
+import (
+	"database/sql"
+	"errors"
+	"net/http"
+
+	"github.com/google/uuid"
+
+	"mgit.msbls.de/m/KanzlAI-mGMT/internal/auth"
+	"mgit.msbls.de/m/KanzlAI-mGMT/internal/models"
+	"github.com/jmoiron/sqlx"
+)
+
+type CaseEventHandler struct {
+	db *sqlx.DB
+}
+
+func NewCaseEventHandler(db *sqlx.DB) *CaseEventHandler {
+	return &CaseEventHandler{db: db}
+}
+
+// Get handles GET /api/case-events/{id}
+func (h *CaseEventHandler) Get(w http.ResponseWriter, r *http.Request) {
+	tenantID, ok := auth.TenantFromContext(r.Context())
+	if !ok {
+		writeError(w, http.StatusUnauthorized, "missing tenant")
+		return
+	}
+
+	eventID, err := uuid.Parse(r.PathValue("id"))
+	if err != nil {
+		writeError(w, http.StatusBadRequest, "invalid event ID")
+		return
+	}
+
+	var event models.CaseEvent
+	err = h.db.GetContext(r.Context(), &event,
+		`SELECT id, tenant_id, case_id, event_type, title, description, event_date, created_by, metadata, created_at, updated_at
+		 FROM case_events
+		 WHERE id = $1 AND tenant_id = $2`, eventID, tenantID)
+	if err != nil {
+		if errors.Is(err, sql.ErrNoRows) {
+			writeError(w, http.StatusNotFound, "case event not found")
+			return
+		}
+		writeError(w, http.StatusInternalServerError, "failed to fetch case event")
+		return
+	}
+
+	writeJSON(w, http.StatusOK, event)
+}

backend/internal/handlers/deadlines.go

@@ -20,6 +20,33 @@ func NewDeadlineHandlers(ds *services.DeadlineService, db *sqlx.DB) *DeadlineHan
 	return &DeadlineHandlers{deadlines: ds, db: db}
 }
 
+// Get handles GET /api/deadlines/{deadlineID}
+func (h *DeadlineHandlers) Get(w http.ResponseWriter, r *http.Request) {
+	tenantID, err := resolveTenant(r, h.db)
+	if err != nil {
+		handleTenantError(w, err)
+		return
+	}
+
+	deadlineID, err := parsePathUUID(r, "deadlineID")
+	if err != nil {
+		writeError(w, http.StatusBadRequest, "invalid deadline ID")
+		return
+	}
+
+	deadline, err := h.deadlines.GetByID(tenantID, deadlineID)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to fetch deadline")
+		return
+	}
+	if deadline == nil {
+		writeError(w, http.StatusNotFound, "deadline not found")
+		return
+	}
+
+	writeJSON(w, http.StatusOK, deadline)
+}
+
 // ListAll handles GET /api/deadlines
 func (h *DeadlineHandlers) ListAll(w http.ResponseWriter, r *http.Request) {
 	tenantID, err := resolveTenant(r, h.db)

backend/internal/handlers/notes.go

@@ -0,0 +1,159 @@
+package handlers
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+
+	"github.com/google/uuid"
+
+	"mgit.msbls.de/m/KanzlAI-mGMT/internal/auth"
+	"mgit.msbls.de/m/KanzlAI-mGMT/internal/services"
+)
+
+type NoteHandler struct {
+	svc *services.NoteService
+}
+
+func NewNoteHandler(svc *services.NoteService) *NoteHandler {
+	return &NoteHandler{svc: svc}
+}
+
+// List handles GET /api/notes?{parent_type}_id={id}
+func (h *NoteHandler) List(w http.ResponseWriter, r *http.Request) {
+	tenantID, ok := auth.TenantFromContext(r.Context())
+	if !ok {
+		writeError(w, http.StatusUnauthorized, "missing tenant")
+		return
+	}
+
+	parentType, parentID, err := parseNoteParent(r)
+	if err != nil {
+		writeError(w, http.StatusBadRequest, err.Error())
+		return
+	}
+
+	notes, err := h.svc.ListByParent(r.Context(), tenantID, parentType, parentID)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to list notes")
+		return
+	}
+
+	writeJSON(w, http.StatusOK, notes)
+}
+
+// Create handles POST /api/notes
+func (h *NoteHandler) Create(w http.ResponseWriter, r *http.Request) {
+	tenantID, ok := auth.TenantFromContext(r.Context())
+	if !ok {
+		writeError(w, http.StatusUnauthorized, "missing tenant")
+		return
+	}
+	userID, _ := auth.UserFromContext(r.Context())
+
+	var input services.CreateNoteInput
+	if err := json.NewDecoder(r.Body).Decode(&input); err != nil {
+		writeError(w, http.StatusBadRequest, "invalid request body")
+		return
+	}
+	if input.Content == "" {
+		writeError(w, http.StatusBadRequest, "content is required")
+		return
+	}
+
+	var createdBy *uuid.UUID
+	if userID != uuid.Nil {
+		createdBy = &userID
+	}
+
+	note, err := h.svc.Create(r.Context(), tenantID, createdBy, input)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to create note")
+		return
+	}
+
+	writeJSON(w, http.StatusCreated, note)
+}
+
+// Update handles PUT /api/notes/{id}
+func (h *NoteHandler) Update(w http.ResponseWriter, r *http.Request) {
+	tenantID, ok := auth.TenantFromContext(r.Context())
+	if !ok {
+		writeError(w, http.StatusUnauthorized, "missing tenant")
+		return
+	}
+
+	noteID, err := uuid.Parse(r.PathValue("id"))
+	if err != nil {
+		writeError(w, http.StatusBadRequest, "invalid note ID")
+		return
+	}
+
+	var req struct {
+		Content string `json:"content"`
+	}
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		writeError(w, http.StatusBadRequest, "invalid request body")
+		return
+	}
+	if req.Content == "" {
+		writeError(w, http.StatusBadRequest, "content is required")
+		return
+	}
+
+	note, err := h.svc.Update(r.Context(), tenantID, noteID, req.Content)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "failed to update note")
+		return
+	}
+	if note == nil {
+		writeError(w, http.StatusNotFound, "note not found")
+		return
+	}
+
+	writeJSON(w, http.StatusOK, note)
+}
+
+// Delete handles DELETE /api/notes/{id}
+func (h *NoteHandler) Delete(w http.ResponseWriter, r *http.Request) {
+	tenantID, ok := auth.TenantFromContext(r.Context())
+	if !ok {
+		writeError(w, http.StatusUnauthorized, "missing tenant")
+		return
+	}
+
+	noteID, err := uuid.Parse(r.PathValue("id"))
+	if err != nil {
+		writeError(w, http.StatusBadRequest, "invalid note ID")
+		return
+	}
+
+	if err := h.svc.Delete(r.Context(), tenantID, noteID); err != nil {
+		writeError(w, http.StatusNotFound, "note not found")
+		return
+	}
+
+	w.WriteHeader(http.StatusNoContent)
+}
+
+// parseNoteParent extracts the parent type and ID from query parameters.
+func parseNoteParent(r *http.Request) (string, uuid.UUID, error) {
+	params := map[string]string{
+		"case_id":       "case",
+		"deadline_id":   "deadline",
+		"appointment_id": "appointment",
+		"case_event_id": "case_event",
+	}
+
+	for param, parentType := range params {
+		if v := r.URL.Query().Get(param); v != "" {
+			id, err := uuid.Parse(v)
+			if err != nil {
+				return "", uuid.Nil, fmt.Errorf("invalid %s", param)
+			}
+			return parentType, id, nil
+		}
+	}
+
+	return "", uuid.Nil, fmt.Errorf("one of case_id, deadline_id, appointment_id, or case_event_id is required")
+}

backend/internal/models/note.go

@@ -0,0 +1,20 @@
+package models
+
+import (
+	"time"
+
+	"github.com/google/uuid"
+)
+
+type Note 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,omitempty"`
+	DeadlineID    *uuid.UUID `db:"deadline_id" json:"deadline_id,omitempty"`
+	AppointmentID *uuid.UUID `db:"appointment_id" json:"appointment_id,omitempty"`
+	CaseEventID   *uuid.UUID `db:"case_event_id" json:"case_event_id,omitempty"`
+	Content       string     `db:"content" json:"content"`
+	CreatedBy     *uuid.UUID `db:"created_by" json:"created_by,omitempty"`
+	CreatedAt     time.Time  `db:"created_at" json:"created_at"`
+	UpdatedAt     time.Time  `db:"updated_at" json:"updated_at"`
+}

backend/internal/router/router.go

@@ -40,6 +40,7 @@ func New(db *sqlx.DB, authMW *auth.Middleware, cfg *config.Config, calDAVSvc *se
 	// Middleware
 	tenantResolver := auth.NewTenantResolver(tenantSvc)
 
+	noteSvc := services.NewNoteService(db)
 	dashboardSvc := services.NewDashboardService(db)
 
 	// Handlers
@@ -51,6 +52,8 @@ func New(db *sqlx.DB, authMW *auth.Middleware, cfg *config.Config, calDAVSvc *se
 	ruleH := handlers.NewDeadlineRuleHandlers(deadlineRuleSvc)
 	calcH := handlers.NewCalculateHandlers(calculator, deadlineRuleSvc)
 	dashboardH := handlers.NewDashboardHandler(dashboardSvc)
+	noteH := handlers.NewNoteHandler(noteSvc)
+	eventH := handlers.NewCaseEventHandler(db)
 	docH := handlers.NewDocumentHandler(documentSvc)
 
 	// Public routes
@@ -85,6 +88,7 @@ func New(db *sqlx.DB, authMW *auth.Middleware, cfg *config.Config, calDAVSvc *se
 	scoped.HandleFunc("DELETE /api/parties/{partyId}", partyH.Delete)
 
 	// Deadlines
+	scoped.HandleFunc("GET /api/deadlines/{deadlineID}", deadlineH.Get)
 	scoped.HandleFunc("GET /api/deadlines", deadlineH.ListAll)
 	scoped.HandleFunc("GET /api/cases/{caseID}/deadlines", deadlineH.ListForCase)
 	scoped.HandleFunc("POST /api/cases/{caseID}/deadlines", deadlineH.Create)
@@ -101,11 +105,21 @@ func New(db *sqlx.DB, authMW *auth.Middleware, cfg *config.Config, calDAVSvc *se
 	scoped.HandleFunc("POST /api/deadlines/calculate", calcH.Calculate)
 
 	// Appointments
+	scoped.HandleFunc("GET /api/appointments/{id}", apptH.Get)
 	scoped.HandleFunc("GET /api/appointments", apptH.List)
 	scoped.HandleFunc("POST /api/appointments", apptH.Create)
 	scoped.HandleFunc("PUT /api/appointments/{id}", apptH.Update)
 	scoped.HandleFunc("DELETE /api/appointments/{id}", apptH.Delete)
 
+	// Case events
+	scoped.HandleFunc("GET /api/case-events/{id}", eventH.Get)
+
+	// Notes
+	scoped.HandleFunc("GET /api/notes", noteH.List)
+	scoped.HandleFunc("POST /api/notes", noteH.Create)
+	scoped.HandleFunc("PUT /api/notes/{id}", noteH.Update)
+	scoped.HandleFunc("DELETE /api/notes/{id}", noteH.Delete)
+
 	// Dashboard
 	scoped.HandleFunc("GET /api/dashboard", dashboardH.Get)
 

backend/internal/services/dashboard_service.go

@@ -42,6 +42,7 @@ type UpcomingDeadline struct {
 	ID         uuid.UUID `json:"id" db:"id"`
 	Title      string    `json:"title" db:"title"`
 	DueDate    string    `json:"due_date" db:"due_date"`
+	CaseID     uuid.UUID `json:"case_id" db:"case_id"`
 	CaseNumber string    `json:"case_number" db:"case_number"`
 	CaseTitle  string    `json:"case_title" db:"case_title"`
 	Status     string    `json:"status" db:"status"`
@@ -56,8 +57,10 @@ type UpcomingAppointment struct {
 }
 
 type RecentActivity struct {
+	ID         uuid.UUID  `json:"id" db:"id"`
 	EventType  *string    `json:"event_type" db:"event_type"`
 	Title      string     `json:"title" db:"title"`
+	CaseID     uuid.UUID  `json:"case_id" db:"case_id"`
 	CaseNumber string     `json:"case_number" db:"case_number"`
 	EventDate  *time.Time `json:"event_date" db:"event_date"`
 }
@@ -109,7 +112,7 @@ func (s *DashboardService) Get(ctx context.Context, tenantID uuid.UUID) (*Dashbo
 
 	// Upcoming deadlines (next 7 days)
 	deadlineQuery := `
-		SELECT d.id, d.title, d.due_date, c.case_number, c.title AS case_title, d.status
+		SELECT d.id, d.title, d.due_date, d.case_id, c.case_number, c.title AS case_title, d.status
 		FROM deadlines d
 		JOIN cases c ON c.id = d.case_id AND c.tenant_id = d.tenant_id
 		WHERE d.tenant_id = $1 AND d.status = 'pending' AND d.due_date >= $2 AND d.due_date <= $3
@@ -135,7 +138,7 @@ func (s *DashboardService) Get(ctx context.Context, tenantID uuid.UUID) (*Dashbo
 
 	// Recent activity (last 10 case events)
 	activityQuery := `
-		SELECT ce.event_type, ce.title, c.case_number, ce.event_date
+		SELECT ce.id, ce.event_type, ce.title, ce.case_id, c.case_number, ce.event_date
 		FROM case_events ce
 		JOIN cases c ON c.id = ce.case_id AND c.tenant_id = ce.tenant_id
 		WHERE ce.tenant_id = $1

backend/internal/services/note_service.go

@@ -0,0 +1,120 @@
+package services
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+	"time"
+
+	"github.com/google/uuid"
+	"github.com/jmoiron/sqlx"
+
+	"mgit.msbls.de/m/KanzlAI-mGMT/internal/models"
+)
+
+type NoteService struct {
+	db *sqlx.DB
+}
+
+func NewNoteService(db *sqlx.DB) *NoteService {
+	return &NoteService{db: db}
+}
+
+// ListByParent returns all notes for a given parent entity, scoped to tenant.
+func (s *NoteService) ListByParent(ctx context.Context, tenantID uuid.UUID, parentType string, parentID uuid.UUID) ([]models.Note, error) {
+	col, err := parentColumn(parentType)
+	if err != nil {
+		return nil, err
+	}
+
+	query := fmt.Sprintf(
+		`SELECT id, tenant_id, case_id, deadline_id, appointment_id, case_event_id,
+		        content, created_by, created_at, updated_at
+		 FROM notes
+		 WHERE tenant_id = $1 AND %s = $2
+		 ORDER BY created_at DESC`, col)
+
+	var notes []models.Note
+	if err := s.db.SelectContext(ctx, &notes, query, tenantID, parentID); err != nil {
+		return nil, fmt.Errorf("listing notes by %s: %w", parentType, err)
+	}
+	if notes == nil {
+		notes = []models.Note{}
+	}
+	return notes, nil
+}
+
+type CreateNoteInput struct {
+	CaseID        *uuid.UUID `json:"case_id,omitempty"`
+	DeadlineID    *uuid.UUID `json:"deadline_id,omitempty"`
+	AppointmentID *uuid.UUID `json:"appointment_id,omitempty"`
+	CaseEventID   *uuid.UUID `json:"case_event_id,omitempty"`
+	Content       string     `json:"content"`
+}
+
+// Create inserts a new note.
+func (s *NoteService) Create(ctx context.Context, tenantID uuid.UUID, createdBy *uuid.UUID, input CreateNoteInput) (*models.Note, error) {
+	id := uuid.New()
+	now := time.Now().UTC()
+
+	query := `INSERT INTO notes (id, tenant_id, case_id, deadline_id, appointment_id, case_event_id, content, created_by, created_at, updated_at)
+	          VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $9)
+	          RETURNING id, tenant_id, case_id, deadline_id, appointment_id, case_event_id, content, created_by, created_at, updated_at`
+
+	var n models.Note
+	err := s.db.GetContext(ctx, &n, query,
+		id, tenantID, input.CaseID, input.DeadlineID, input.AppointmentID, input.CaseEventID,
+		input.Content, createdBy, now)
+	if err != nil {
+		return nil, fmt.Errorf("creating note: %w", err)
+	}
+	return &n, nil
+}
+
+// Update modifies a note's content.
+func (s *NoteService) Update(ctx context.Context, tenantID, noteID uuid.UUID, content string) (*models.Note, error) {
+	query := `UPDATE notes SET content = $1, updated_at = $2
+	          WHERE id = $3 AND tenant_id = $4
+	          RETURNING id, tenant_id, case_id, deadline_id, appointment_id, case_event_id, content, created_by, created_at, updated_at`
+
+	var n models.Note
+	err := s.db.GetContext(ctx, &n, query, content, time.Now().UTC(), noteID, tenantID)
+	if err != nil {
+		if err == sql.ErrNoRows {
+			return nil, nil
+		}
+		return nil, fmt.Errorf("updating note: %w", err)
+	}
+	return &n, nil
+}
+
+// Delete removes a note.
+func (s *NoteService) Delete(ctx context.Context, tenantID, noteID uuid.UUID) error {
+	result, err := s.db.ExecContext(ctx, "DELETE FROM notes WHERE id = $1 AND tenant_id = $2", noteID, tenantID)
+	if err != nil {
+		return fmt.Errorf("deleting note: %w", err)
+	}
+	rows, err := result.RowsAffected()
+	if err != nil {
+		return fmt.Errorf("checking delete result: %w", err)
+	}
+	if rows == 0 {
+		return fmt.Errorf("note not found")
+	}
+	return nil
+}
+
+func parentColumn(parentType string) (string, error) {
+	switch parentType {
+	case "case":
+		return "case_id", nil
+	case "deadline":
+		return "deadline_id", nil
+	case "appointment":
+		return "appointment_id", nil
+	case "case_event":
+		return "case_event_id", nil
+	default:
+		return "", fmt.Errorf("invalid parent type: %s", parentType)
+	}
+}