refactor(api): 将WebChatUpgrade接口更新为Upgrade_V2并调整相关字段

更新API端点从WebChatUpgrade改为Upgrade_V2，同时将响应字段Data更名为Message
修改涉及README文档、API规范、控制器和客户端代码，保持接口变更的一致性

src/apiClient.js

@@ -16,16 +16,16 @@ const triggerUpgrade = async (roomtype_id, host_list, fileName) => {
         params.append('host_list_str', JSON.stringify(host_list));
         params.append('fileName', fileName);
 
-        console.log('[WebChatUpgrade] Request', {
+        console.log('[Upgrade_V2] Request', {
             roomtype_id,
             host_list_str: host_list,
             fileName
         });
-        const response = await apiClient.post('/WebChatUpgrade', params);
-        console.log('[WebChatUpgrade] Response', response.data);
+        const response = await apiClient.post('/Upgrade_V2', params);
+        console.log('[Upgrade_V2] Response', response.data);
         return response.data;
     } catch (error) {
-        console.error('Error calling WebChatUpgrade:', error.message);
+        console.error('Error calling Upgrade_V2:', error.message);
         throw error;
     }
 };