Add Facebook social login

resources/js/admin/mobile/__tests__/LoginPage.test.tsx

@@ -103,13 +103,15 @@ vi.mock('lucide-react', () => ({
 import MobileLoginPage from '../LoginPage';
 
 describe('MobileLoginPage', () => {
-  it('renders Google login button', () => {
+  it('renders OAuth login buttons', () => {
     locationSearch = '?return_to=encoded-value';
 
     render(<MobileLoginPage />);
 
     const googleButton = screen.getByText('Mit Google anmelden');
     expect(googleButton).toBeInTheDocument();
+    const facebookButton = screen.getByText('Mit Facebook anmelden');
+    expect(facebookButton).toBeInTheDocument();
   });
 
   it('shows oauth error details when present', () => {