Fix remap-foods: add missing db_conn import

Generator was failing silently due to undefined db_conn reference.

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

backend/api/routes/videos.py

@@ -311,6 +311,7 @@ def remap_cuisine(_admin: dict = Depends(get_admin_user)):
 def remap_foods(_admin: dict = Depends(get_admin_user)):
     """Re-extract foods_mentioned for all video_restaurants using LLM. SSE progress."""
     from core.extractor import _llm, _parse_json
+    from core.db import conn as db_conn
 
     BATCH = 15