feat: time tracking + billing — hourly rates, time entries, invoices (P1)

Database: time_entries, billing_rates, invoices tables with RLS.
Backend: CRUD services+handlers for time entries, billing rates, invoices.
  - Time entries: list/create/update/delete, summary by case/user/month
  - Billing rates: upsert with auto-close previous, current rate lookup
  - Invoices: create with auto-number (RE-YYYY-NNN), status transitions
    (draft->sent->paid, cancellation), link time entries on invoice create
API: 11 new endpoints under /api/time-entries, /api/billing-rates, /api/invoices
Frontend: Zeiterfassung tab on case detail, /abrechnung overview with filters,
  /abrechnung/rechnungen list+detail with status actions, billing rates settings
Also: resolved merge conflicts between audit-trail and role-based branches,
  added missing types (Notification, AuditLogResponse, NotificationPreferences)

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
-	scoped.HandleFunc("GET /api/audit-log", auditH.List)
+	// Audit log — view requires PermViewAuditLog
+	scoped.HandleFunc("GET /api/audit-log", perm(auth.PermViewAuditLog, 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))