refactor: UniversalListPage externalIsLoading 지원 및 스켈레톤 개선

- UniversalListPage에 externalIsLoading prop 추가
- CardTransactionDetailClient DevFill 자동입력 기능 추가
- 여러 컴포넌트 로딩 상태 처리 개선
- skeleton 컴포넌트 확장

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/components/customer-center/InquiryManagement/InquiryDetailClientV2.tsx

@@ -25,7 +25,7 @@ import {
   deletePost,
 } from '../shared/actions';
 import { transformApiToComment } from '../shared/types';
-import { ContentLoadingSpinner } from '@/components/ui/loading-spinner';
+import { DetailPageSkeleton } from '@/components/ui/skeleton';
 import { ErrorCard } from '@/components/ui/error-card';
 
 type DetailMode = 'view' | 'edit' | 'create';
@@ -165,7 +165,7 @@ export function InquiryDetailClientV2({ inquiryId, initialMode }: InquiryDetailC
 
   // ===== 로딩 상태 =====
   if (isLoading) {
-    return <ContentLoadingSpinner />;
+    return <DetailPageSkeleton sections={1} fieldsPerSection={4} />;
   }
 
   // ===== 에러 상태 =====