feat(frontend-auth): complete NextAuth.js Keycloak integration with middleware, hooks, and API utility

- Add middleware.ts for route protection (redirects unauthenticated users to /login)
- Add useActiveClub() hook for managing active club context (localStorage + session)
- Add apiClient() fetch wrapper with automatic Authorization + X-Tenant-Id headers
- Configure vitest with jsdom environment and global test setup
- Add comprehensive test coverage: 16/16 tests passing (hooks + API utility)
- Install test dependencies: vitest, @testing-library/react, @vitejs/plugin-react, happy-dom

Task 10 COMPLETE - all acceptance criteria met

frontend/src/test/setup.ts

@@ -0,0 +1,12 @@
+import '@testing-library/jest-dom';
+import { vi } from 'vitest';
+
+const localStorageMock = {
+  getItem: vi.fn(),
+  setItem: vi.fn(),
+  removeItem: vi.fn(),
+  clear: vi.fn(),
+};
+
+global.localStorage = localStorageMock as any;
+