style(ui): 统一页面字号间距与状态样式

lib/pages/auth/auth_view.dart

@@ -9,6 +9,7 @@ import '../../core/data/remote/api_client.dart';
 import '../../core/data/services/auth_controller.dart';
 import '../../core/platform/haptics.dart';
 import '../../core/theme/app_colors.dart';
+import '../../core/theme/app_dimens.dart';
 import '../../core/theme/app_theme.dart';
 import '../../l10n/app_localizations.dart';
 import 'auth_logic.dart';
@@ -19,8 +20,9 @@ part 'auth_form_widgets.dart';
 const double _minTapTarget = 44;
 const double _brandMarkSize = 48;
 const double _contentMaxWidth = 440;
-const double _cardRadius = 20;
-const double _cardPadding = 20;
+// Auth keeps its approved 20px card silhouette.
+const double _cardRadius = AppDimens.authCardRadius;
+const double _cardPadding = AppDimens.cardPadding;
 const double _cardBorderWidth = 1;
 const double _fieldHeight = 52;
 const double _fieldRadius = 14;
@@ -163,9 +165,9 @@ class _AuthPageState extends State<AuthPage> {
                   keyboardDismissBehavior:
                       ScrollViewKeyboardDismissBehavior.onDrag,
                   padding: EdgeInsets.fromLTRB(
-                    20,
+                    AppDimens.pageHorizontal,
                     12,
-                    20,
+                    AppDimens.pageHorizontal,
                     28 + MediaQuery.viewInsetsOf(context).bottom,
                   ),
                   children: [

lib/pages/auth/auth_widgets.dart

@@ -103,7 +103,7 @@ class _AuthCard extends StatelessWidget {
             l10n.authSubtitle,
             style: const TextStyle(
               color: AppColors.muted,
-              fontSize: 13,
+              fontSize: AppDimens.body,
               height: 1.45,
             ),
           ),