always block desktop settings page if video connection exists (#10224)

1. Always block desktop settings page if video connection exists, both mouse event and key event are blocked..
2. Server control page always block key event.

Signed-off-by: 21pages <sunboeasy@gmail.com>

flutter/lib/models/state_model.dart

@@ -18,6 +18,7 @@ class StateGlobal {
   final RxDouble _windowBorderWidth = RxDouble(kWindowBorderWidth);
   final RxBool showRemoteToolBar = false.obs;
   final svcStatus = SvcStatus.notReady.obs;
+  final RxInt videoConnCount = 0.obs;
   final RxBool isFocused = false.obs;
   // for mobile and web
   bool isInMainPage = true;