fix: 修复CozeService初始化时get_bot_config缺少参数的问题

- 移除 __init__ 中对 get_bot_config() 的无参数调用
- 改为在需要时根据 session_type 动态获取 bot_config
- 修复 _get_bot_id_by_type 方法使用正确的配置获取方式

backend/app/services/ai/coze/service.py

@@ -43,13 +43,16 @@ class CozeService:
 
     def __init__(self):
         self.client = get_coze_client()
-        self.bot_config = get_bot_config()
         self.workspace_id = get_workspace_id()
 
         # 内存中的会话存储（生产环境应使用 Redis）
         self._sessions: Dict[str, CozeSession] = {}
         self._messages: Dict[str, List[CozeMessage]] = {}
     
+    def _get_bot_config(self, session_type: str) -> Dict[str, Any]:
+        """根据会话类型获取 Bot 配置"""
+        return get_bot_config(session_type)
+
     async def create_session(
         self, request: CreateSessionRequest
     ) -> CreateSessionResponse:
@@ -211,12 +214,15 @@ class CozeService:
 
     def _get_bot_id_by_type(self, session_type: SessionType) -> str:
         """根据会话类型获取 Bot ID"""
-        mapping = {
-            SessionType.COURSE_CHAT: self.bot_config["course_chat"],
-            SessionType.TRAINING: self.bot_config["training"],
-            SessionType.EXAM: self.bot_config["exam"],
+        # 将 SessionType 枚举映射到配置字符串
+        type_mapping = {
+            SessionType.COURSE_CHAT: "course_chat",
+            SessionType.TRAINING: "training",
+            SessionType.EXAM: "training",  # 考试类型使用训练 bot
         }
-        return mapping.get(session_type, self.bot_config["training"])
+        config_type = type_mapping.get(session_type, "training")
+        bot_config = get_bot_config(config_type)
+        return bot_config["bot_id"]
 
     def _get_session(self, session_id: str) -> Optional[CozeSession]:
         """获取会话"""