feat: 구독 페이지 API 호출 사용량 표시 연동

- UsageApiData에 api_calls 타입 추가
- transformApiToFrontend에서 apiCallsUsed/apiCallsLimit 처리
- 기본 제한값 10,000으로 설정

src/components/settings/SubscriptionManagement/SubscriptionManagement.tsx

@@ -22,6 +22,9 @@ import type { SubscriptionInfo } from './types';
 import { PLAN_LABELS } from './types';
 import { requestDataExport, cancelSubscription } from './actions';
 
+// ===== 기본 저장공간 (10GB) =====
+const DEFAULT_STORAGE_LIMIT = 10 * 1024 * 1024 * 1024; // 10GB in bytes
+
 // ===== 기본값 (API 실패시 사용) =====
 const defaultSubscription: SubscriptionInfo = {
   lastPaymentDate: '',
@@ -31,9 +34,11 @@ const defaultSubscription: SubscriptionInfo = {
   userCount: 0,
   userLimit: null,
   storageUsed: 0,
-  storageLimit: 0,
+  storageLimit: DEFAULT_STORAGE_LIMIT,
+  storageUsedFormatted: '0 B',
+  storageLimitFormatted: '10 GB',
   apiCallsUsed: 0,
-  apiCallsLimit: 0,
+  apiCallsLimit: 10000,
 };
 
 // ===== 날짜 포맷 함수 =====
@@ -202,8 +207,8 @@ export function SubscriptionManagement({ initialData }: SubscriptionManagementPr
                   <div className="flex-1">
                     <Progress value={storageProgress} className="h-2" />
                   </div>
-                  <div className="text-sm text-blue-600 min-w-[100px] text-right">
-                    {subscription.storageUsed} TB /{subscription.storageLimit} TB
+                  <div className="text-sm text-blue-600 min-w-[120px] text-right">
+                    {subscription.storageUsedFormatted} / {subscription.storageLimitFormatted}
                   </div>
                 </div>