fix: 마켓 API 요청 필드명 snake_case→camelCase 수정

서버는 assetId/listingId(camelCase)를 기대하나
asset_id/listing_id(snake_case)로 보내고 있어 검증 실패.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/api/chain.js

@@ -64,13 +64,13 @@ function idempotentPost(path, body) {
 }
 
 export async function listOnMarket(assetId, price) {
-  return idempotentPost('/api/chain/market/list', { asset_id: assetId, price });
+  return idempotentPost('/api/chain/market/list', { assetId, price });
 }
 
 export async function buyFromMarket(listingId) {
-  return idempotentPost('/api/chain/market/buy', { listing_id: listingId });
+  return idempotentPost('/api/chain/market/buy', { listingId });
 }
 
 export async function cancelListing(listingId) {
-  return idempotentPost('/api/chain/market/cancel', { listing_id: listingId });
+  return idempotentPost('/api/chain/market/cancel', { listingId });
 }