Add managed UIKit iOS client

clients/apple/dotnet/VoiceCat.iOS/SceneDelegate.cs

@@ -0,0 +1,22 @@
+using Foundation;
+using UIKit;
+
+namespace VoiceCat.iOS;
+
+[Register("SceneDelegate")]
+internal sealed class SceneDelegate : UIResponder, IUIWindowSceneDelegate
+{
+    [Export("window")]
+    public UIWindow? Window { get; set; }
+
+    [Export("scene:willConnectToSession:options:")]
+    public void WillConnect(UIScene scene, UISceneSession session, UISceneConnectionOptions options)
+    {
+        if (scene is not UIWindowScene windowScene) return;
+        Window = new(windowScene) { RootViewController = new RootViewController(AppModel.Shared) };
+        Window.MakeKeyAndVisible();
+    }
+
+    [Export("sceneDidEnterBackground:")]
+    public void DidEnterBackground(UIScene scene) => AppModel.Shared.Save();
+}