Add web dashboard OTA upload with live progress.

Share UART OTA logic between CLI and serve via POST /api/ota, WebSocket progress events, and a dashboard upload UI showing the running partition.

Co-authored-by: Cursor <cursoragent@cursor.com>

goTool/cmd_serve.go

@@ -40,7 +40,7 @@ func runServe(portName string, baud int, args []string) error {
 	go runPoller(link, portName, hub, *interval, stop)
 
 	mux := http.NewServeMux()
-	mountServeAPI(mux, link)
+	mountServeAPI(mux, link, hub)
 	mux.HandleFunc("/ws", func(w http.ResponseWriter, r *http.Request) {
 		conn, err := wsUpgrader.Upgrade(w, r, nil)
 		if err != nil {