fix: 重命名变量以避免与内置函数冲突

1. 将 Message 类中的 time 参数重命名为 timestamp，避免与 Python 内置模块 time 冲突
2. 在消息处理相关函数中统一使用 timestamp 变量名称
3. 优化 message_storage 查询条件构建方式

🤖 Generated with [Claude Code](https://claude.ai/code)

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

src/plugins/PFC/conversation.py

@@ -124,7 +124,7 @@ class Conversation:
             return Message(
                 message_id=msg_dict["message_id"],
                 chat_stream=chat_stream,
-                time=msg_dict["time"],
+                timestamp=msg_dict["time"],
                 user_info=user_info,
                 processed_plain_text=msg_dict.get("processed_plain_text", ""),
                 detailed_plain_text=msg_dict.get("detailed_plain_text", ""),

src/plugins/PFC/message_storage.py

@@ -51,11 +51,9 @@ class MongoDBMessageStorage(MessageStorage):
     """MongoDB消息存储实现"""
 
     async def get_messages_after(self, chat_id: str, message_time: float) -> List[Dict[str, Any]]:
-        query = {"chat_id": chat_id}
+        query = {"chat_id": chat_id, "time": {"$gt": message_time}}
         # print(f"storage_check_message: {message_time}")
 
-        query["time"] = {"$gt": message_time}
-
         return list(db.messages.find(query).sort("time", 1))
 
     async def get_messages_before(self, chat_id: str, time_point: float, limit: int = 5) -> List[Dict[str, Any]]: