fix: 企微 API 通过代理绕过 IP 白名单限制，补充错误日志

- 新增 WECHAT_API_BASE_URL 配置项，支持企微 API 代理转发
- _send_message 增加 API 错误日志（errcode + errmsg）
- _get_access_token 增加失败日志
- handle_text 不再为空，返回菜单引导提示
- 防重入触发时通知用户等待时间
- menu.py API 调用统一使用配置化的 base URL

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

app/wechat/menu.py

@@ -71,7 +71,7 @@ class MenuManager:
         if not token:
             return False
 
-        url = "https://qyapi.weixin.qq.com/cgi-bin/menu/create"
+        url = f"{settings.wechat_api_base_url}/cgi-bin/menu/create"
         params = {"access_token": token, "agentid": int(settings.wechat_agent_id)}
 
         async with httpx.AsyncClient(timeout=15) as client:
@@ -88,7 +88,7 @@ class MenuManager:
         if not token:
             return False
 
-        url = "https://qyapi.weixin.qq.com/cgi-bin/menu/delete"
+        url = f"{settings.wechat_api_base_url}/cgi-bin/menu/delete"
         params = {"access_token": token, "agentid": int(settings.wechat_agent_id)}
 
         async with httpx.AsyncClient(timeout=15) as client:
@@ -101,7 +101,7 @@ class MenuManager:
         if not token:
             return None
 
-        url = "https://qyapi.weixin.qq.com/cgi-bin/menu/get"
+        url = f"{settings.wechat_api_base_url}/cgi-bin/menu/get"
         params = {"access_token": token, "agentid": int(settings.wechat_agent_id)}
 
         async with httpx.AsyncClient(timeout=15) as client: