fix: force-close user connections on removal, fix UDP upload/download counters, use self-hosted releases

- service.go: call CloseUserConnections() before RemoveUsers() so banned/reset
  users are disconnected immediately instead of waiting for natural timeout
  (upstream issue #32, PR pending 4+ months)

- conntracker.go: swap UnwrapPacketReader/Writer upload/download counters for
  UDP PacketConn path — Reader=upload, Writer=download to match TCP path
  (upstream issue #55)

- xbctl/main.go: change downloadBase to JP01 Gitea so xbctl upgrade pulls
  self-hosted patched releases instead of upstream

cmd/xbctl/main.go

@@ -30,7 +30,7 @@ const (
 	serviceName            = "xboard-node.service"
 	serviceFilePath        = "/etc/systemd/system/xboard-node.service"
 	defaultInstallRoot     = "/etc/xboard-node"
-	downloadBase           = "https://github.com/cedar2025/xboard-node/releases"
+	downloadBase           = "http://103.112.1.141:3000/will/xboard-node"
 )
 
 var (
@@ -593,10 +593,8 @@ func ensureRoot(cmd string) error {
 }
 
 func resolveDownloadURL(artifact, version string) string {
-	if version == "latest" {
-		return downloadBase + "/latest/download/" + artifact
-	}
-	return downloadBase + "/download/" + version + "/" + artifact
+	// Gitea release download URL: {base}/releases/download/{tag}/{file}
+	return downloadBase + "/releases/download/" + version + "/" + artifact
 }
 
 func downloadFile(url, dest string) error {