feat: i18n 개선 및 userfront 로그인/로케일 보완

userfront/test/locale_storage_web_test.dart

@@ -0,0 +1,88 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:userfront/core/i18n/locale_storage.dart';
+import 'package:userfront/core/i18n/locale_storage_web.dart' as locale_web;
+
+import 'helpers/web_storage.dart';
+
+void main() {
+  setUp(() {
+    locale_web.LocaleStorageImpl.forceMemoryStorageForTests(false);
+    locale_web.LocaleStorageImpl.forceSessionStorageForTests(false);
+    if (webStorage.isWeb) {
+      webStorage.clear();
+      webStorage.clearSession();
+    }
+  });
+
+  tearDown(() {
+    locale_web.LocaleStorageImpl.forceMemoryStorageForTests(false);
+    locale_web.LocaleStorageImpl.forceSessionStorageForTests(false);
+    if (webStorage.isWeb) {
+      webStorage.clear();
+      webStorage.clearSession();
+    }
+  });
+
+  test(
+    'localStorage write/read (웹)',
+    () {
+      if (!webStorage.isWeb) {
+        return;
+      }
+
+      LocaleStorage.write('ko');
+      expect(webStorage.get('locale'), 'ko');
+      expect(LocaleStorage.read(), 'ko');
+    },
+    skip: !webStorage.isWeb,
+  );
+
+  test(
+    'legacy key에서 locale로 마이그레이션 (웹)',
+    () {
+      if (!webStorage.isWeb) {
+        return;
+      }
+
+      webStorage.set('baron_locale', 'en');
+      expect(LocaleStorage.read(), 'en');
+      expect(webStorage.get('locale'), 'en');
+      expect(webStorage.get('baron_locale'), isNull);
+    },
+    skip: !webStorage.isWeb,
+  );
+
+  test(
+    'localStorage 접근이 차단되면 메모리 fallback (웹)',
+    () {
+      if (!webStorage.isWeb) {
+        return;
+      }
+
+      locale_web.LocaleStorageImpl.forceMemoryStorageForTests(true);
+
+      LocaleStorage.write('en');
+      expect(webStorage.get('locale'), isNull);
+      expect(webStorage.getSession('locale'), isNull);
+      expect(LocaleStorage.read(), 'en');
+    },
+    skip: !webStorage.isWeb,
+  );
+
+  test(
+    'localStorage 접근이 차단되면 sessionStorage로 fallback (웹)',
+    () {
+      if (!webStorage.isWeb) {
+        return;
+      }
+
+      locale_web.LocaleStorageImpl.forceSessionStorageForTests(true);
+
+      LocaleStorage.write('ko');
+      expect(webStorage.get('locale'), isNull);
+      expect(webStorage.getSession('locale'), 'ko');
+      expect(LocaleStorage.read(), 'ko');
+    },
+    skip: !webStorage.isWeb,
+  );
+}