fix : API_URL -> NEXT_PUBLIC_API_URL 일괄 변경

src/components/items/ItemDetailClient.tsx

@@ -86,7 +86,7 @@ function getStorageUrl(path: string | undefined): string | null {
     return path;
   }
   // 상대 경로인 경우
-  const apiUrl = process.env.API_URL || '';
+  const apiUrl = process.env.NEXT_PUBLIC_API_URL || '';
   return `${apiUrl}/storage/${path}`;
 }