feat: add payment card grouping and analysis

lib/controllers/detail_screen_controller.dart

@@ -34,6 +34,7 @@ class DetailScreenController extends ChangeNotifier {
   late String _billingCycle;
   late DateTime _nextBillingDate;
   String? _selectedCategoryId;
+  String? _selectedPaymentCardId;
   late String _currency;
   bool _isLoading = false;
 
@@ -46,6 +47,7 @@ class DetailScreenController extends ChangeNotifier {
   String get billingCycle => _billingCycle;
   DateTime get nextBillingDate => _nextBillingDate;
   String? get selectedCategoryId => _selectedCategoryId;
+  String? get selectedPaymentCardId => _selectedPaymentCardId;
   String get currency => _currency;
   bool get isLoading => _isLoading;
   bool get isEventActive => _isEventActive;
@@ -74,6 +76,13 @@ class DetailScreenController extends ChangeNotifier {
     }
   }
 
+  set selectedPaymentCardId(String? value) {
+    if (_selectedPaymentCardId != value) {
+      _selectedPaymentCardId = value;
+      notifyListeners();
+    }
+  }
+
   set currency(String value) {
     if (_currency != value) {
       _currency = value;
@@ -153,6 +162,7 @@ class DetailScreenController extends ChangeNotifier {
     _billingCycle = subscription.billingCycle;
     _nextBillingDate = subscription.nextBillingDate;
     _selectedCategoryId = subscription.categoryId;
+    _selectedPaymentCardId = subscription.paymentCardId;
     _currency = subscription.currency;
 
     // Event State 초기화
@@ -415,6 +425,7 @@ class DetailScreenController extends ChangeNotifier {
         BillingDateUtil.ensureFutureDate(originalDateOnly, _billingCycle);
     subscription.nextBillingDate = adjustedNext;
     subscription.categoryId = _selectedCategoryId;
+    subscription.paymentCardId = _selectedPaymentCardId;
     subscription.currency = _currency;
 
     // 이벤트 정보 업데이트