feat(ui): 登录页重设计并统一弹框主题渐变外壳

lib/core/widgets/auth_gate.dart

@@ -5,6 +5,7 @@ import '../../l10n/app_localizations.dart';
 import '../../pages/auth/auth_view.dart';
 import '../data/services/auth_controller.dart';
 import '../theme/app_colors.dart';
+import 'app_glow_panel.dart';
 
 /// 打开登录 / 注册页（沿用现有 Navigator 风格，不引路由库）
 Future<void> openAuthPage(BuildContext context, {bool signUpMode = false}) {
@@ -23,11 +24,11 @@ Future<bool> ensureSignedIn(BuildContext context) async {
   final l10n = AppLocalizations.of(context)!;
   final go = await showModalBottomSheet<bool>(
     context: context,
-    backgroundColor: AppColors.card,
-    shape: const RoundedRectangleBorder(
-      borderRadius: BorderRadius.vertical(top: Radius.circular(18)),
-    ),
-    builder: (sheetContext) => SafeArea(
+    backgroundColor: AppColors.transparent,
+    builder: (sheetContext) => AppGlowPanel(
+      borderRadius: const BorderRadius.vertical(top: Radius.circular(18)),
+      border: false,
+      child: SafeArea(
       child: Padding(
         padding: const EdgeInsets.fromLTRB(20, 18, 20, 20),
         child: Column(
@@ -71,6 +72,7 @@ Future<bool> ensureSignedIn(BuildContext context) async {
           ],
         ),
       ),
+      ),
     ),
   );