fix: resolve all 65 pre-existing frontend test failures (318/318 passing)

- Remove duplicate vi.mock(@/api/hooks) in SettingsRoles.test.tsx that overrode forceUpdate logic
- SettingsRoles mock: use vi.hoisted for shared forceUpdateRef between useRoles and useUpdateRole
- SettingsRoles mock: use plain async functions instead of vi.fn().mockImplementation for mutations

frontend/src/__tests__/shell/AppShell.test.tsx

@@ -3,6 +3,7 @@ import { describe, it, expect, vi } from 'vitest';
 import { render, screen, within } from '@testing-library/react';
 import { MemoryRouter, Route, Routes } from 'react-router-dom';
 import { AppShell } from '@/components/layout/AppShell';
+import { useAuthStore } from '@/store/authStore';
 
 vi.mock('@/api/hooks', () => ({
   useLogout: () => ({ mutateAsync: vi.fn(), isPending: false }),
@@ -21,6 +22,24 @@ function renderWithRouter(initialPath = '/dashboard') {
 }
 
 describe('AppShell', () => {
+  beforeEach(() => {
+    useAuthStore.setState({
+      isAuthenticated: true,
+      user: {
+        id: '1',
+        email: 'max@test.de',
+        first_name: 'Max',
+        last_name: 'Mustermann',
+        role: 'admin',
+        avatar_url: null,
+        tenants: [
+          { id: 't1', name: 'Firma Alpha', slug: 'alpha' },
+          { id: 't2', name: 'Firma Beta', slug: 'beta' },
+        ],
+      },
+      currentTenant: { id: 't1', name: 'Firma Alpha', slug: 'alpha' },
+    });
+  });
   it('renders sidebar, topbar, and content area', () => {
     renderWithRouter();
     expect(screen.getByTestId('app-shell')).toBeInTheDocument();