[优化] 添加 Relay frps 连接和代理计数字段，重构相关逻辑以支持监控和可观测性

openflare_server/controller/relay.go

@@ -26,6 +26,7 @@ func RelayHeartbeat(c *gin.Context) {
 	if !bindJSON(c, &payload) {
 		return
 	}
+	payload.IP = service.ResolveReportedNodeIP(payload.IP, c.Request.RemoteAddr)
 	authNode, ok := c.Get("relay_node")
 	if !ok {
 		respondUnauthorized(c, "无权进行此操作")