fix: 调整mac和win的初始尺寸，固定初始化尺寸

windows/runner/main.cpp

@@ -85,7 +85,7 @@ int APIENTRY wWinMain(_In_ HINSTANCE instance, _In_opt_ HINSTANCE prev,
 
   FlutterWindow window(project);
   Win32Window::Point origin(10, 10);
-  Win32Window::Size size(1280, 720);
+  Win32Window::Size size(375, 800);
   if (!window.Create(L"HiFastVPN", origin, size)) {
     return EXIT_FAILURE;
   }