fix(app-shell): instabile Zustands-Selektoren veroursachten haengende Lazy-Routen ("Dashboard loads forever") — Root Cause: moduleMenuOrder()/visibleModuleKeys() erzeugten bei jedem getSnapshot neue Map/Set-Objekte

frontend/src/components/layout/Sidebar.tsx

@@ -73,7 +73,16 @@ export function Sidebar() {
   const { hasPermission } = usePermission();
   const user = useAuthStore((state) => state.user);
   const { isModuleVisible } = useWorkspace();
-  const moduleMenuOrder = useWorkspaceStore(s => s.moduleMenuOrder());
+  // NOTE: never select object-factory calls in a Zustand selector —
+  // `s.moduleMenuOrder()` creates a NEW Map on every getSnapshot call,
+  // which destabilizes useSyncExternalStore and causes a synchronous
+  // re-render loop that starves pending Suspense (lazy route) commits
+  // ("Dashboard loads forever" root cause). Select stable state and
+  // derive with useMemo instead.
+  const workspaceContext = useWorkspaceStore(s => s.context);
+  const moduleMenuOrder = useMemo(() => new Map(
+    (workspaceContext?.modules ?? []).map(m => [m.module_key, m.menu_order] as const),
+  ), [workspaceContext]);
 
   // Use hasPermission directly — permissions are loaded via useUserPermissions hook
   const canAccess = (perm?: string): boolean => {

frontend/src/hooks/useWorkspace.ts

@@ -1,4 +1,4 @@
-import { useEffect, useCallback } from 'react';
+import { useEffect, useCallback, useMemo } from 'react';
 import { useMyWorkspaces, useWorkspaceContext } from '@/api/hooks/workspaces';
 import { useWorkspaceStore, type WorkspaceInfo, type WorkspaceContextState } from '@/store/workspaceStore';
 import { useAuthStore } from '@/store/authStore';
@@ -62,7 +62,13 @@ export function useWorkspace() {
     return isModuleVisibleFromStore(moduleKey, isSystemAdmin);
   }, [isModuleVisibleFromStore, isSystemAdmin]);
 
-  const visibleModuleKeys = useWorkspaceStore(s => s.visibleModuleKeys());
+  // NOTE: derive from the stable `context` reference via useMemo —
+  // `s.visibleModuleKeys()` would create a NEW Set on every getSnapshot
+  // call, destabilizing useSyncExternalStore (same root cause as the
+  // Sidebar moduleMenuOrder infinite re-render loop).
+  const visibleModuleKeys = useMemo(() => new Set(
+    (context?.modules ?? []).filter(m => m.is_visible !== false).map(m => m.module_key),
+  ), [context]);
 
   return {
     activeWorkspaceId,

frontend/src/routes/index.tsx

@@ -94,8 +94,6 @@ const router = createBrowserRouter([
     path: '/login',
     element: <LoginPage />,
   },
-  {
-  },
   {
     path: '/dms-standalone',
     element: <ErrorBoundary>{withSuspense(<DmsStandalonePage />)}</ErrorBoundary>,