fix: Replace ineffective break with return in WebSocket close handler

SA4011 staticcheck warning - switch cases break implicitly in Go,
so break was a no-op. Using return to properly exit handleWebSocket
when client sends close message.

main.go

@@ -516,7 +516,7 @@ func (s *Server) handleWebSocket(w http.ResponseWriter, r *http.Request) {
 		case "state":
 			s.handleWSState(conn)
 		case "close":
-			break
+			return
 		default:
 			errMsg, _ := json.Marshal(map[string]string{"error": "unknown message type: " + msg.Type})
 			conn.WriteMessage(websocket.TextMessage, errMsg)