Add per-slave ESP-NOW OTA progress over UART and fix dashboard updates.

Expose OTA_SLAVE_PROGRESS on the master, track per-slave state during
distribution, run ESP-NOW OTA in a background task so the host can poll
while slaves update, and show master/slave progress in the dashboard
with table layout and faster WebSocket refresh during uploads.

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

goTool/cmd_ota_progress.go

@@ -0,0 +1,28 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+)
+
+func runOtaProgress(sp *serialPort, args []string) error {
+	fs := flag.NewFlagSet("ota-progress", flag.ExitOnError)
+	clientID := fs.Uint("client", 0, "slave client id (0 = all in session)")
+	if err := fs.Parse(args); err != nil {
+		return err
+	}
+
+	r, err := QueryOtaSlaveProgress(sp, uint32(*clientID))
+	if err != nil {
+		return err
+	}
+
+	fmt.Printf("active=%v total=%d aggregate=%d slaves=%d\n",
+		r.GetActive(), r.GetTotalBytes(), r.GetAggregateBytes(), r.GetSlaveCount())
+	for _, s := range r.GetSlaves() {
+		fmt.Printf("  slave %d: %d / %d bytes status=%d error=%d\n",
+			s.GetClientId(), s.GetBytesWritten(), s.GetTotalBytes(),
+			s.GetStatus(), s.GetError())
+	}
+	return nil
+}