T07b: frontend feature pages — companies + contacts + settings + audit + dashboard + search

- 11 new feature pages (CompaniesList/Detail/Form, ContactsList/Detail/Form,
  SettingsProfile/Roles/Users, AuditLog, GlobalSearchResults)
- 3 page updates (Dashboard with StatCard+ActivityFeed, Settings with tree nav+Outlet,
  TopBar with SearchDropdown)
- 13 new routes in routes/index.tsx
- i18n updates (de.json + en.json) with companies/contacts/settings/audit/search keys
- 12 new test files + 2 existing test fixes (TopBar, AppShell)
- 7 shared components (DataGrid, Tabs, SearchDropdown, CsvImportDialog, StatCard,
  ActivityFeed, UnsavedChangesGuard)
- 16 new API hooks in hooks.ts
- Verification: 141 tests pass, build succeeds, tsc --noEmit clean

frontend/src/__tests__/AuditLog.test.tsx

@@ -0,0 +1,51 @@
+import React from 'react';
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { render, screen } from '@testing-library/react';
+import { MemoryRouter } from 'react-router-dom';
+import { AuditLogPage } from '@/pages/AuditLog';
+
+let mockReturnValue: any = {
+  data: {
+    items: [
+      { timestamp: '2025-06-29T10:00:00Z', user: 'anna.schmidt', action: 'create', entity: 'company', entity_id: '1', details: 'Firma erstellt' },
+    ],
+    total: 1,
+  },
+  isLoading: false,
+  isError: false,
+};
+
+vi.mock('@/api/hooks', () => ({
+  useAuditLog: () => mockReturnValue,
+}));
+
+describe('AuditLogPage', () => {
+  beforeEach(() => {
+    mockReturnValue = {
+      data: {
+        items: [
+          { timestamp: '2025-06-29T10:00:00Z', user: 'anna.schmidt', action: 'create', entity: 'company', entity_id: '1', details: 'Firma erstellt' },
+        ],
+        total: 1,
+      },
+      isLoading: false,
+      isError: false,
+    };
+  });
+
+  it('renders audit log page', () => {
+    render(<MemoryRouter><AuditLogPage /></MemoryRouter>);
+    expect(screen.getByTestId('audit-log-page')).toBeInTheDocument();
+  });
+
+  it('renders audit log table via DataGrid', () => {
+    render(<MemoryRouter><AuditLogPage /></MemoryRouter>);
+    expect(screen.getByTestId('audit-log-grid')).toBeInTheDocument();
+  });
+
+  it('handles 404 error gracefully', () => {
+    mockReturnValue = { data: undefined, isLoading: false, isError: true };
+    render(<MemoryRouter><AuditLogPage /></MemoryRouter>);
+    expect(screen.getByText(/nicht verf/)).toBeInTheDocument();
+  });
+});