uf 액션 토스트 공통화 및 SnackBar 제거

userfront/lib/features/auth/presentation/consent_screen.dart

@@ -4,6 +4,7 @@ import 'package:userfront/i18n.dart';
 import 'package:userfront/core/i18n/locale_utils.dart';
 import 'package:userfront/core/services/auth_proxy_service.dart';
 import 'package:userfront/core/services/web_window.dart';
+import 'package:userfront/core/ui/toast_service.dart';
 
 class ConsentScreen extends StatefulWidget {
   final String consentChallenge;
@@ -187,16 +188,11 @@ class _ConsentScreenState extends State<ConsentScreen> {
       } catch (e) {
         setState(() => _isSubmitting = false);
         if (mounted) {
-          ScaffoldMessenger.of(context).showSnackBar(
-            SnackBar(
-              content: Text(
-                tr(
-                  'msg.userfront.consent.cancel.error',
-                  fallback:
-                      'An error occurred while cancelling consent: {{error}}',
-                  params: {'error': '$e'},
-                ),
-              ),
+          ToastService.error(
+            tr(
+              'msg.userfront.consent.cancel.error',
+              fallback: 'An error occurred while cancelling consent: {{error}}',
+              params: {'error': '$e'},
             ),
           );
         }
@@ -419,7 +415,7 @@ class _ConsentScreenState extends State<ConsentScreen> {
                         )
                       : Text(
                           tr('ui.userfront.consent.accept'),
-                          style: TextStyle(
+                          style: const TextStyle(
                             fontSize: 16,
                             fontWeight: FontWeight.bold,
                           ),