修改引用逻辑，修改长期记忆bug

rag_core/store/postgres.py

@@ -4,12 +4,10 @@
 使用 asyncpg 实现真正的异步 PostgreSQL 文档存储，支持高并发访问。
 """
 
-from __future__ import annotations
-
 import asyncio
 import json
 import logging
-from typing import List, Dict, Any, Optional, Iterator, Tuple, Sequence, cast
+from typing import List, Dict, Any, Optional, Iterator, Tuple, Sequence
 
 from langchain_core.documents import Document
 from langchain_core.stores import BaseStore
@@ -18,7 +16,6 @@ import asyncpg
 
 logger = logging.getLogger(__name__)
 
-
 class PostgresDocStore(BaseStore[str, Any]):
     """
     异步 PostgreSQL 文档存储实现。