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/context.go

@@ -9,19 +9,11 @@ import (
 type contextKey string
 
 const (
-<<<<<<< HEAD
 	userIDKey    contextKey = "user_id"
 	tenantIDKey  contextKey = "tenant_id"
+	userRoleKey  contextKey = "user_role"
 	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
 )
 
 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