feat(ws): 新增WebSocket实时通信支持与SSE独立服务

重构中间件结构，新增ws模块实现WebSocket流程执行实时推送
将SSE服务拆分为独立端口监听，默认8866
优化前端流式模式切换，支持WS/SSE协议选择
统一流式事件处理逻辑，完善错误处理与取消机制
更新Cargo.toml依赖，添加WebSocket相关库
调整代码组织结构，规范导入分组与注释

backend/src/flow/log_handler.rs

@@ -17,9 +17,9 @@ pub trait FlowLogHandler: Send + Sync {
     async fn log_error(&self, flow_id: &str, flow_code: Option<&str>, input: &Value, error_msg: &str, operator: Option<(i64, String)>, started_at: DateTime<FixedOffset>, duration_ms: i64) -> anyhow::Result<()>;
     
     /// 记录流程执行失败（包含部分输出与累计日志）
-    async fn log_error_detail(&self, flow_id: &str, flow_code: Option<&str>, input: &Value, output: &Value, logs: &[String], error_msg: &str, operator: Option<(i64, String)>, started_at: DateTime<FixedOffset>, duration_ms: i64) -> anyhow::Result<()> {
+    async fn log_error_detail(&self, _flow_id: &str, _flow_code: Option<&str>, _input: &Value, _output: &Value, _logs: &[String], error_msg: &str, _operator: Option<(i64, String)>, _started_at: DateTime<FixedOffset>, _duration_ms: i64) -> anyhow::Result<()> {
         // 默认实现：退化为仅错误信息
-        self.log_error(flow_id, flow_code, input, error_msg, operator, started_at, duration_ms).await
+        self.log_error(_flow_id, _flow_code, _input, error_msg, _operator, _started_at, _duration_ms).await
     }
     
     /// 记录流程执行成功