feat: i18n 개선 및 userfront 로그인/로케일 보완

userfront/test/helpers/web_storage_stub.dart

@@ -0,0 +1,21 @@
+class WebStorage {
+  bool get isWeb => false;
+
+  String? get(String key) => null;
+
+  void set(String key, String value) {}
+
+  String? getSession(String key) => null;
+
+  void setSession(String key, String value) {}
+
+  void removeSession(String key) {}
+
+  void clearSession() {}
+
+  void remove(String key) {}
+
+  void clear() {}
+}
+
+final webStorage = WebStorage();