refactor(wechatclawbot): 渠道管理改为模块方法契约，endpoint 不再接触客户端对象

- 收消息方向保持 Telegram 模式：模块自建连接轮询网关，转发本地消息 API
- 管理方向（状态/二维码/退出/连通性）封装为 wechatclawbot_status 等模块契约方法，
  实例解析与临时客户端回退封闭在模块内部，统一返回 {success, message} dict
- 新建 NotificationChain 薄分发链，MessageChain 移除全部 clawbot 方法
- notification endpoint 改为纯 chain 调用，不再获取任何客户端对象

app/chain/message.py

@@ -1850,58 +1850,4 @@ class MessageChain(ChainBase):
             return base64.b64decode(payload)
         except Exception as e:
             logger.error(e)
-            return None
-
-    def get_wechatclawbot_client(
-            self,
-            source: Optional[str] = None,
-            fallback_source: Optional[str] = None,
-            WECHATCLAWBOT_BASE_URL: Optional[str] = None,
-            WECHATCLAWBOT_DEFAULT_TARGET: Optional[str] = None,
-            WECHATCLAWBOT_ADMINS: Optional[str] = None,
-            WECHATCLAWBOT_POLL_TIMEOUT: Optional[int] = None,
-            allow_temporary: bool = False,
-    ):
-        """获取已加载的微信 ClawBot 客户端，必要时退回到临时客户端。"""
-        source_name = str(source or "").strip() or None
-
-        client = self.run_module(
-            "wechatclawbot_client",
-            source=source,
-            fallback_source=fallback_source,
-        )
-        if client:
-            return client, None
-
-        if allow_temporary:
-            temp_client = self.run_module(
-                "wechatclawbot_temp_client",
-                source=source_name or str(fallback_source or "").strip() or None,
-                WECHATCLAWBOT_BASE_URL=WECHATCLAWBOT_BASE_URL,
-                WECHATCLAWBOT_DEFAULT_TARGET=WECHATCLAWBOT_DEFAULT_TARGET,
-                WECHATCLAWBOT_ADMINS=WECHATCLAWBOT_ADMINS,
-                WECHATCLAWBOT_POLL_TIMEOUT=WECHATCLAWBOT_POLL_TIMEOUT,
-            )
-            if temp_client:
-                return temp_client, None
-
-        if source_name:
-            return None, f"未找到名为 {source_name} 的微信 ClawBot 通知配置"
-        return None, "微信 ClawBot 通知未启用或配置尚未保存，请先保存并启用当前渠道"
-
-    def migrate_wechatclawbot_cache(
-            self,
-            old_name: str,
-            new_name: str,
-            cleanup_old: bool = False,
-            overwrite: bool = False,
-    ):
-        """在通知名称变更时迁移对应的微信 ClawBot 登录缓存。"""
-        return self.run_module(
-            "wechatclawbot_migrate_cache",
-            old_name=old_name,
-            new_name=new_name,
-            cleanup_old=cleanup_old,
-            overwrite=overwrite,
-        )
-
+            return None