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__/contacts/ContactDetail.test.tsx

@@ -0,0 +1,29 @@
+import React from 'react';
+import { describe, it, expect, vi } from 'vitest';
+import { render, screen } from '@testing-library/react';
+import { MemoryRouter } from 'react-router-dom';
+import { ContactDetailPage } from '@/pages/ContactDetail';
+
+vi.mock('@/api/hooks', () => ({
+  useContact: () => ({
+    data: {
+      id: '1', first_name: 'Max', last_name: 'Mustermann',
+      email: 'max@example.com', phone: '+49 30 12345678',
+      position: 'CEO', company_id: '1', company_name: 'TestCorp GmbH',
+      created_at: '2025-01-01T00:00:00Z', updated_at: '2025-01-01T00:00:00Z',
+    },
+    isLoading: false,
+  }),
+}));
+
+describe('ContactDetailPage', () => {
+  it('renders the detail page', () => {
+    render(<MemoryRouter initialEntries={['/contacts/1']}><ContactDetailPage /></MemoryRouter>);
+    expect(screen.getByTestId('contact-detail-page')).toBeInTheDocument();
+  });
+
+  it('renders tabs', () => {
+    render(<MemoryRouter initialEntries={['/contacts/1']}><ContactDetailPage /></MemoryRouter>);
+    expect(screen.getByRole('tablist')).toBeInTheDocument();
+  });
+});