修复了数据库无法读取记忆和知识的问题，以及图片保存问题

src/plugins/chat/utils.py

@@ -88,13 +88,13 @@ def get_cloest_chat_from_db(db, length: int, timestamp: str):
         list: 消息记录列表，每个记录包含时间和文本信息
     """
     chat_records = []
-    closest_record = db.db.messages.find_one({"time": {"$lte": timestamp}}, sort=[('time', -1)])
+    closest_record = db.messages.find_one({"time": {"$lte": timestamp}}, sort=[('time', -1)])
     
     if closest_record:            
         closest_time = closest_record['time']
         chat_id = closest_record['chat_id']  # 获取chat_id
         # 获取该时间戳之后的length条消息，保持相同的chat_id
-        chat_records = list(db.db.messages.find(
+        chat_records = list(db.messages.find(
             {
                 "time": {"$gt": closest_time},
                 "chat_id": chat_id  # 添加chat_id过滤
@@ -128,7 +128,7 @@ async def get_recent_group_messages(db, chat_id:str, limit: int = 12) -> list:
     """
 
     # 从数据库获取最近消息
-    recent_messages = list(db.db.messages.find(
+    recent_messages = list(db.messages.find(
         {"chat_id": chat_id},
     ).sort("time", -1).limit(limit))
 
@@ -162,7 +162,7 @@ async def get_recent_group_messages(db, chat_id:str, limit: int = 12) -> list:
 
 
 def get_recent_group_detailed_plain_text(db, chat_stream_id: int, limit: int = 12, combine=False):
-    recent_messages = list(db.db.messages.find(
+    recent_messages = list(db.messages.find(
         {"chat_id": chat_stream_id},
         {
             "time": 1,  # 返回时间字段