feat: dashboard widgets, auth fix, profile names, dynamic groups

- Add VehicleDashboardCard: self-contained widget modelled after
  AtemschutzDashboardCard, shows einsatzbereit ratio and inspection
  warnings inline; replaces StatsCard + InspectionAlerts in Dashboard

- Add EquipmentDashboardCard: consolidated equipment status widget
  showing only aggregated counts (no per-item listing); replaces
  EquipmentAlerts component in Dashboard

- Fix auth race condition: add authInitialized flag to api.ts so 401
  responses during initial token validation no longer trigger a
  spurious redirect to /login; save intended destination before login
  redirect and restore it after successful auth callback

- Fix profile firstname/lastname: add extractNames() helper to
  auth.controller.ts that falls back to splitting userinfo.name when
  Authentik does not provide separate given_name/family_name fields;
  applied on both create and update paths

- Dynamic groups endpoint: replace hardcoded KNOWN_GROUPS array in
  events.controller.ts with a DB query (SELECT DISTINCT unnest
  (authentik_groups) FROM users); known slugs get German labels via
  lookup map, unknown slugs are humanized automatically

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/contexts/AuthContext.tsx

@@ -3,6 +3,7 @@ import { AuthContextType, AuthState, User } from '../types/auth.types';
 import { authService } from '../services/auth';
 import { getToken, setToken, removeToken, getUser, setUser, removeUser } from '../utils/storage';
 import { useNotification } from './NotificationContext';
+import { setAuthInitialized } from '../services/api';
 
 const AuthContext = createContext<AuthContextType | undefined>(undefined);
 
@@ -47,6 +48,8 @@ export const AuthProvider: React.FC<AuthProviderProps> = ({ children }) => {
             isAuthenticated: false,
             isLoading: false,
           });
+        } finally {
+          setAuthInitialized(true);
         }
       } else {
         setState({
@@ -55,6 +58,7 @@ export const AuthProvider: React.FC<AuthProviderProps> = ({ children }) => {
           isAuthenticated: false,
           isLoading: false,
         });
+        setAuthInitialized(true);
       }
     };