fix(realestate-lab): 최종 리뷰 이슈 수정 — FK CASCADE, 단일 연결, 동시성 가드

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

realestate-lab/app/main.py

@@ -1,5 +1,6 @@
 import os
 import logging
+import threading
 from contextlib import asynccontextmanager
 from fastapi import BackgroundTasks, FastAPI, Query, HTTPException
 from fastapi.middleware.cors import CORSMiddleware
@@ -110,9 +111,18 @@ def api_announcement_delete(ann_id: int):
 
 # ── 수집 API ─────────────────────────────────────────────────────────────────
 
+_collect_lock = threading.Lock()
+
+
 def _run_collect_and_match():
-    collect_all()
-    run_matching()
+    if not _collect_lock.acquire(blocking=False):
+        logger.info("수집 이미 진행 중 — 건너뜀")
+        return
+    try:
+        collect_all()
+        run_matching()
+    finally:
+        _collect_lock.release()
 
 
 @app.post("/api/realestate/collect")