feat(auth): 优化登录页布局与字段反馈

lib/l10n/app_localizations_en.dart

@@ -652,6 +652,10 @@ class AppLocalizationsEn extends AppLocalizations {
   @override
   String get authSubtitle => 'Sign in with your email and password.';
 
+  @override
+  String get authSignUpSubtitle =>
+      'Create an account to keep your list, history, and progress.';
+
   @override
   String get authBrandTagline => 'Short dramas made for Indonesia';