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/accounting/BadDebtCollection/BadDebtDetailClientV2.tsx

@@ -12,7 +12,7 @@ import { useRouter, useSearchParams } from 'next/navigation';
 import { BadDebtDetail } from './BadDebtDetail';
 import { getBadDebtById } from './actions';
 import type { BadDebtRecord } from './types';
-import { ContentLoadingSpinner } from '@/components/ui/loading-spinner';
+import { DetailPageSkeleton } from '@/components/ui/skeleton';
 import { ErrorCard } from '@/components/ui/error-card';
 import { toast } from 'sonner';
 
@@ -86,7 +86,7 @@ export function BadDebtDetailClientV2({ recordId, initialMode }: BadDebtDetailCl
 
   // 로딩 중
   if (isLoading) {
-    return <ContentLoadingSpinner text="악성채권 정보를 불러오는 중..." />;
+    return <DetailPageSkeleton sections={2} fieldsPerSection={6} />;
   }
 
   // 에러 발생 (view/edit 모드에서)