fix(halacha): import asyncpg — undefined-name guard (annotation ב-_acquire_global_lock)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

mcp-server/src/legal_mcp/services/halacha_extractor.py

@@ -26,6 +26,8 @@ import logging
 import re
 from uuid import UUID
 
+import asyncpg
+
 from legal_mcp import config
 from legal_mcp.config import parse_llm_json
 from legal_mcp.services import (