refactor: standardize tsconfig paths, update deprecation settings, and format user creation timestamp to ISO string

apps/backend/src/modules/user/services/user.service.ts

@@ -14,6 +14,6 @@ export function getUserProfile(user: User): UserProfile {
     email: user.email,
     role: (user as any).role || 'member',
     avatarUrl: user.image || getGravatarUrl(user.email),
-    createdAt: user.createdAt,
+    createdAt: user.createdAt.toISOString(),
   };
 }