userfront gateway 분리.

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

@@ -21,6 +21,7 @@ class _QRScanScreenState extends State<QRScanScreen> {
   bool _isScanned = false;
   bool _isCheckingSession = false;
   bool _isProcessing = false;
+  bool _isRequestingCamera = false;
   bool? _isSuccess;
   String? _resultMessage;
 
@@ -100,10 +101,7 @@ class _QRScanScreenState extends State<QRScanScreen> {
         }
         if (sessionToken == null && !usesCookie) {
           if (mounted) {
-             ScaffoldMessenger.of(context).showSnackBar(
-              const SnackBar(content: Text('로그인이 필요합니다.'), backgroundColor: Colors.red),
-            );
-            context.pop();
+            context.go('/signin?notice=qr_login_required');
           }
           return;
         }
@@ -148,6 +146,28 @@ class _QRScanScreenState extends State<QRScanScreen> {
     controller.start();
   }
 
+  Future<void> _requestCameraPermission() async {
+    if (_isRequestingCamera) return;
+    setState(() => _isRequestingCamera = true);
+    try {
+      await controller.start();
+    } catch (e) {
+      _log.warning('Camera permission request failed: $e');
+      if (mounted) {
+        ScaffoldMessenger.of(context).showSnackBar(
+          const SnackBar(
+            content: Text('카메라 권한 요청에 실패했습니다. 브라우저/OS 설정을 확인해주세요.'),
+            backgroundColor: Colors.red,
+          ),
+        );
+      }
+    } finally {
+      if (mounted) {
+        setState(() => _isRequestingCamera = false);
+      }
+    }
+  }
+
   Widget _buildResultView() {
     final success = _isSuccess == true;
     final icon = success ? Icons.check_circle_outline : Icons.error_outline;
@@ -207,13 +227,30 @@ class _QRScanScreenState extends State<QRScanScreen> {
                   controller: controller,
                   onDetect: _onDetect,
                   errorBuilder: (context, error) {
+                    final isPermissionDenied = error.errorCode ==
+                        MobileScannerErrorCode.permissionDenied;
                     return Center(
                       child: Column(
                         mainAxisAlignment: MainAxisAlignment.center,
                         children: [
                           const Icon(Icons.error, color: Colors.red, size: 50),
                           const SizedBox(height: 10),
-                          Text('Camera Error: ${error.errorCode}'),
+                          Text(
+                            isPermissionDenied
+                                ? '카메라 권한이 필요합니다.'
+                                : '카메라 오류: ${error.errorCode}',
+                          ),
+                          const SizedBox(height: 12),
+                          FilledButton(
+                            onPressed: _isRequestingCamera
+                                ? null
+                                : _requestCameraPermission,
+                            child: Text(
+                              _isRequestingCamera
+                                  ? '요청 중...'
+                                  : '카메라 권한 요청하기',
+                            ),
+                          ),
                         ],
                       ),
                     );