Add LED ring control per client and broadcast over REST and WebSocket.

Solid color mode fills all ring LEDs; master routes UART commands to slaves
via ESPNOW_LED_RING. goTool exposes POST /api/led-ring, WebSocket set_led_ring,
and a dashboard LED panel with master/slave/all targets.

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

goTool/client_api.go

@@ -377,6 +377,16 @@ func (s *serialPort) LedRing(req *pb.LedRingProgressRequest) (*pb.LedRingProgres
 	return s.ledRingProgress(req)
 }
 
+func (m *managedSerial) LedRing(req *pb.LedRingProgressRequest) (*pb.LedRingProgressResponse, error) {
+	var resp *pb.LedRingProgressResponse
+	err := m.withPort(func(sp *serialPort) error {
+		var e error
+		resp, e = sp.LedRing(req)
+		return e
+	})
+	return resp, err
+}
+
 func (s *serialPort) FindMe(clientID uint32) (*pb.EspNowFindMeResponse, error) {
 	return s.espnowFindMe(clientID)
 }