feat: reporting dashboard — case stats, deadline compliance, workload, billing (P1)

Backend:
- ReportingService with aggregation queries (CTEs, FILTER clauses)
- 4 API endpoints: /api/reports/{cases,deadlines,workload,billing}
- Date range filtering via ?from=&to= query params

Frontend:
- /berichte page with 4 tabs: Akten, Fristen, Auslastung, Abrechnung
- recharts: bar/pie/line charts for all report types
- Date range picker, CSV export, print-friendly view
- Sidebar nav entry with BarChart3 icon

Also resolves merge conflicts between role-based, notification, and
audit trail branches, and adds missing TS types (AuditLogResponse,
Notification, NotificationPreferences).

backend/internal/auth/middleware.go

@@ -35,36 +35,8 @@ 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 +45,6 @@ func (m *Middleware) RequireAuth(next http.Handler) http.Handler {
 		}
 		ctx = ContextWithRequestInfo(ctx, ip, r.UserAgent())
 
->>>>>>> mai/knuth/p0-audit-trail-append
 		next.ServeHTTP(w, r.WithContext(ctx))
 	})
 }