feat: add payment card grouping and analysis

lib/providers/subscription_provider.dart

@@ -118,6 +118,7 @@ class SubscriptionProvider extends ChangeNotifier {
     required DateTime nextBillingDate,
     String? websiteUrl,
     String? categoryId,
+    String? paymentCardId,
     bool isAutoDetected = false,
     int repeatCount = 1,
     DateTime? lastPaymentDate,
@@ -136,6 +137,7 @@ class SubscriptionProvider extends ChangeNotifier {
         nextBillingDate: nextBillingDate,
         websiteUrl: websiteUrl,
         categoryId: categoryId,
+        paymentCardId: paymentCardId,
         isAutoDetected: isAutoDetected,
         repeatCount: repeatCount,
         lastPaymentDate: lastPaymentDate,
@@ -268,17 +270,22 @@ class SubscriptionProvider extends ChangeNotifier {
   }
 
   /// 총 월간 지출을 계산합니다. (로케일별 기본 통화로 환산)
-  Future<double> calculateTotalExpense({String? locale}) async {
-    if (_subscriptions.isEmpty) return 0.0;
+  Future<double> calculateTotalExpense({
+    String? locale,
+    List<SubscriptionModel>? subset,
+  }) async {
+    final targetSubscriptions = subset ?? _subscriptions;
+    if (targetSubscriptions.isEmpty) return 0.0;
 
     // locale이 제공되지 않으면 현재 로케일 사용
     final targetCurrency =
         locale != null ? CurrencyUtil.getDefaultCurrency(locale) : 'KRW'; // 기본값
 
-    debugPrint('[calculateTotalExpense] 계산 시작 - 타겟 통화: $targetCurrency');
+    debugPrint('[calculateTotalExpense] 계산 시작 - 타겟 통화: $targetCurrency, '
+        '대상 구독: ${targetSubscriptions.length}개');
     double total = 0.0;
 
-    for (final subscription in _subscriptions) {
+    for (final subscription in targetSubscriptions) {
       final currentPrice = subscription.currentPrice;
       debugPrint('[calculateTotalExpense] ${subscription.serviceName}: '
           '$currentPrice ${subscription.currency} (이벤트 적용: ${subscription.isCurrentlyInEvent})');
@@ -292,15 +299,19 @@ class SubscriptionProvider extends ChangeNotifier {
       total += converted ?? currentPrice;
     }
 
-    debugPrint('[calculateTotalExpense] 총 지출 계산 완료: $total $targetCurrency');
+    debugPrint('[calculateTotalExpense] 총 지출 계산 완료: $total '
+        '$targetCurrency (대상 ${targetSubscriptions.length}개)');
     return total;
   }
 
   /// 최근 6개월의 월별 지출 데이터를 반환합니다. (로케일별 기본 통화로 환산)
-  Future<List<Map<String, dynamic>>> getMonthlyExpenseData(
-      {String? locale}) async {
+  Future<List<Map<String, dynamic>>> getMonthlyExpenseData({
+    String? locale,
+    List<SubscriptionModel>? subset,
+  }) async {
     final now = DateTime.now();
     final List<Map<String, dynamic>> monthlyData = [];
+    final targetSubscriptions = subset ?? _subscriptions;
 
     // locale이 제공되지 않으면 현재 로케일 사용
     final targetCurrency =
@@ -321,7 +332,7 @@ class SubscriptionProvider extends ChangeNotifier {
       }
 
       // 해당 월에 활성화된 구독 계산
-      for (final subscription in _subscriptions) {
+      for (final subscription in targetSubscriptions) {
         if (isCurrentMonth) {
           // 현재 월인 경우: 모든 활성 구독 포함 (calculateTotalExpense와 동일하게)
           final cost = subscription.currentPrice;