fix: add status field to service list/detail APIs, unify observeStats retry pattern, fix router bugs

- api: add fillServiceStatus helper and call it from getServiceList/getService
  so status field appears in service list and detail API responses
- observeStats: unify retry pattern across all 9 handlers (http, http2, masque,
  relay, router, socks4, socks5, tungo, tunnel) — buffer events on failure,
  continue to skip fresh collection, clear on success; fix event-loss bug
  where interim events were dropped during retry cycles
- handler/router: check WriteTo/Write return errors in associate.go and
  entrypoint.go; fix DelConnector and ConnectorPool.Del using RLock instead
  of Lock (write under read lock); remove unused fields t and cancel

api/config_service.go

@@ -43,6 +43,13 @@ func getServiceList(ctx *gin.Context) {
 
 	list := config.Global().Services
 
+	for _, svc := range list {
+		if svc == nil {
+			continue
+		}
+		fillServiceStatus(svc)
+	}
+
 	var resp getServiceListResponse
 	resp.Data = serviceList{
 		Count: len(list),
@@ -89,6 +96,7 @@ func getService(ctx *gin.Context) {
 			continue
 		}
 		if service.Name == req.Service {
+			fillServiceStatus(service)
 			resp.Data = service
 		}
 	}