perf(travel-proxy): 배치 DB 연결 + nginx sync timeout 600s

- db.py: batch_sync_album, batch_mark_thumbs_done 추가
- indexer.py: 앨범 단위 배치 동기화로 전환
- nginx: /api/travel/ proxy_read_timeout 600s 추가

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

nginx/default.conf

@@ -91,6 +91,7 @@ server {
 	proxy_set_header X-Real-IP $remote_addr;
 	proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
 	proxy_set_header X-Forwarded-Proto $scheme;
+	proxy_read_timeout 600s;
 	proxy_pass http://travel-proxy:8000/api/travel/;
   }