이벤트 가져오기 위젯 테스트 추가 및 테스트 훅 도입

mobile/lib/screens/subscription/subscription_details_screen.dart

@@ -136,7 +136,7 @@ class _SubscriptionDetailsScreenState extends State<SubscriptionDetailsScreen> {
                 color: Colors.white,
                 boxShadow: [
                   BoxShadow(
-                    color: Colors.black.withOpacity(0.1),
+                    color: Colors.black.withValues(alpha: 0.1),
                     blurRadius: 10,
                     offset: const Offset(0, -5),
                   ),
@@ -207,7 +207,7 @@ class _SubscriptionDetailsScreenState extends State<SubscriptionDetailsScreen> {
                           vertical: 2,
                         ),
                         decoration: BoxDecoration(
-                          color: Colors.amber.withOpacity(0.1),
+                          color: Colors.amber.withValues(alpha: 0.1),
                           borderRadius: BorderRadius.circular(12),
                           border: Border.all(color: Colors.amber),
                         ),
@@ -349,6 +349,8 @@ class _SubscriptionDetailsScreenState extends State<SubscriptionDetailsScreen> {
   }
 
   Future<void> _subscribe(BuildContext context) async {
+    final messenger = ScaffoldMessenger.of(context);
+    final navigator = Navigator.of(context);
     setState(() {
       _isLoading = true;
     });
@@ -361,12 +363,12 @@ class _SubscriptionDetailsScreenState extends State<SubscriptionDetailsScreen> {
       );
 
       if (success && mounted) {
-        ScaffoldMessenger.of(context).showSnackBar(
+        messenger.showSnackBar(
           const SnackBar(content: Text('구독이 성공적으로 완료되었습니다')),
         );
-        Navigator.of(context).pop(); // 상세 화면 닫기
+        navigator.pop(); // 상세 화면 닫기
       } else if (mounted) {
-        ScaffoldMessenger.of(context).showSnackBar(
+        messenger.showSnackBar(
           SnackBar(
             content: Text(subscriptionService.error ?? '구독 처리 중 오류가 발생했습니다'),
             backgroundColor: Colors.red,
@@ -375,7 +377,7 @@ class _SubscriptionDetailsScreenState extends State<SubscriptionDetailsScreen> {
       }
     } catch (e) {
       if (mounted) {
-        ScaffoldMessenger.of(context).showSnackBar(
+        messenger.showSnackBar(
           SnackBar(
             content: Text('오류: $e'),
             backgroundColor: Colors.red,