feat: sprint 3 — profil utilisateur, badge plan, dropdown Header

- AuthContext.User : plan? { slug, name, level } | null
- UserBadge : nickname + badge plan.slug (fallback free)
- Header : dropdown click (Profil / Déconnexion) + click-outside
- ProfilePage : infos compte, badge plan, edit nickname (PATCH /users/me + re-fetch /auth/me → setUser)
- App : route /profile protégée
- useAuth : réexporte depuis AuthContext, fin de la dérive

frontend/src/hooks/useAuth.ts

@@ -1,38 +1,4 @@
-import { useState, useEffect } from 'react';
-import { apiFetch } from '../lib/api';
-
-export interface User {
-  id: string;
-  email: string | null;
-  nickname: string;
-  subscriptionLevel?: number;
-}
-
-interface AuthState {
-  user: User | null;
-  loading: boolean;
-  setUser: (u: User | null) => void;
-}
-
-interface MeResponse {
-  success: boolean;
-  data: { user: User };
-}
-
-export function useAuth(): AuthState {
-  const [user, setUser] = useState<User | null>(null);
-  const [loading, setLoading] = useState(true);
-
-  useEffect(() => {
-    let cancelled = false;
-
-    apiFetch<MeResponse>('/auth/me')
-      .then((res) => { if (!cancelled) setUser(res.data.user); })
-      .catch(() => { if (!cancelled) setUser(null); })
-      .finally(() => { if (!cancelled) setLoading(false); });
-
-    return () => { cancelled = true; };
-  }, []);
-
-  return { user, loading, setUser };
-}
+// Réexporte depuis AuthContext — source unique de vérité auth.
+// Ne pas dupliquer User ou la logique de fetch ici.
+export type { User } from '../context/AuthContext';
+export { useAuthContext as useAuth } from '../context/AuthContext';