userfront로 리펙토링 완료

userfront/lib/core/notifiers/auth_notifier.dart

@@ -0,0 +1,9 @@
+import 'package:flutter/foundation.dart';
+
+class AuthNotifier extends ChangeNotifier {
+  static final AuthNotifier instance = AuthNotifier();
+
+  void notify() {
+    notifyListeners();
+  }
+}