CUB-203: add WebSocket client scaffold for OpenClaw gateway v3

go-backend/cmd/server/main.go

@@ -69,11 +69,20 @@ func main() {
 		PollInterval: cfg.GatewayPollInterval,
 	}, agentRepo, broker)
 
+	// ── WebSocket client (connects to OpenClaw gateway WS v3) ─────────────
+	wsClient := gateway.NewWSClient(gateway.WSConfig{
+		URL:       cfg.WSGatewayURL,
+		AuthToken: cfg.WSGatewayToken,
+	}, agentRepo, broker, logger)
+
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
 
 	go gwClient.Start(ctx)
 
+	// Start WS client in background; logs connection status
+	go wsClient.Start(ctx)
+
 	// ── Server ─────────────────────────────────────────────────────────────
 	srv := &http.Server{
 		Addr:         fmt.Sprintf(":%d", cfg.Port),