Usun symulowane logowanie przez Google i Facebook

Endpoint /api/auth/social byl atrapa bez prawdziwego OAuth: wydawal token
sesji dla dowolnego adresu e-mail podanego w zadaniu, bez hasla. Podanie
adresu administratora dawalo pelna sesje z rola ADMIN.

Na tym etapie logowanie ma byc wylacznie dla uzytkownikow systemu (e-mail
i haslo), wiec usuwam je w calosci:

- backend: endpoint, wpis permitAll w SecurityConfig, AuthService.socialLogin
  z pomocnikami i DTO SocialLoginRequest. Enum AuthProvider zostaje, bo
  istniejace konta moga miec GOOGLE/FACEBOOK.
- frontend: przyciski Google/Facebook w formularzach logowania i rejestracji,
  socialLogin w AuthContext oraz osierocone style.

Test regresyjny AuthControllerTest nie uruchomi sie jeszcze na H2 - start
kontekstu wywraca sie na split_part w SQL naprawiajacym nicki (ten sam blad
dotyczy istniejacego contextLoads). Zweryfikowane recznie na stacku
z PostgreSQL: /api/auth/social -> 403, logowanie e-mailem -> 200.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

frontend/src/auth.tsx

@@ -104,7 +104,6 @@ type AuthContextValue = {
   loading: boolean;
   login: (email: string, password: string) => Promise<AuthUser>;
   register: (email: string, password: string, fullName: string, details?: RegisterDetails) => Promise<RegisterPending>;
-  socialLogin: (provider: Exclude<AuthProviderName, 'LOCAL'>) => Promise<AuthUser>;
   activateAccount: (token: string) => Promise<void>;
   resendActivation: (email: string) => Promise<void>;
   forgotPassword: (email: string) => Promise<void>;
@@ -266,15 +265,6 @@ export function AuthProvider({ children }: { children: ReactNode }) {
     [],
   );
 
-  const socialLogin = useCallback(
-    async (provider: Exclude<AuthProviderName, 'LOCAL'>) =>
-      applyAuth(await apiFetch<AuthResponse>('/auth/social', {
-        method: 'POST',
-        body: JSON.stringify({ provider }),
-      })),
-    [applyAuth],
-  );
-
   const activateAccount = useCallback(async (token: string) => {
     await apiFetch<void>('/auth/activate', { method: 'POST', body: JSON.stringify({ token }) });
   }, []);
@@ -372,11 +362,11 @@ export function AuthProvider({ children }: { children: ReactNode }) {
 
   const value = useMemo<AuthContextValue>(
     () => ({
-      user, token, loading, login, register, socialLogin,
+      user, token, loading, login, register,
       activateAccount, resendActivation, forgotPassword, resetPassword, verifyPhone, resendPhoneOtp,
       updateProfile, changePassword, verifyPassword, passwordCooldown, deleteAccount, loadSettings, loadSearchPreferences, saveSettings, refreshUser, logout,
     }),
-    [user, token, loading, login, register, socialLogin,
+    [user, token, loading, login, register,
       activateAccount, resendActivation, forgotPassword, resetPassword, verifyPhone, resendPhoneOtp,
       updateProfile, changePassword, verifyPassword, passwordCooldown, deleteAccount, loadSettings, loadSearchPreferences, saveSettings, refreshUser, logout],
   );