Warn before software closed; fix bug on first run

Also put settings into proper dir

src/MainWindow.axaml.cs

@@ -1,4 +1,9 @@
+using System;
+using System.Threading.Tasks;
+using Avalonia;
 using Avalonia.Controls;
+using Avalonia.Controls.ApplicationLifetimes;
+using DialogHostAvalonia;
 using MayShow.Interfaces;
 using MayShow.ViewModels;
 
@@ -10,6 +15,60 @@ public partial class MainWindow : Window, ITopLevelGrabber
     {
         InitializeComponent();
         DataContext = new MainWindowViewModel(this);
+
+        Closing += WindowIsClosing;
+
+        var lifetime = Application.Current?.ApplicationLifetime as IClassicDesktopStyleApplicationLifetime;
+        // lifetime?.ShutdownRequested += ApplicationIsShuttingDown;
+    }
+
+    private async void WindowIsClosing(object? sender, WindowClosingEventArgs e)
+    {
+        e.Cancel = true; // async -> need to cancel immediately
+        if (await CheckIfClosePossible())
+        {
+            Closing -= WindowIsClosing;
+            var lifetime = Application.Current?.ApplicationLifetime as IClassicDesktopStyleApplicationLifetime;
+            lifetime?.ShutdownRequested -= ApplicationIsShuttingDown;
+            Close();
+        }
+    }
+
+    private async void ApplicationIsShuttingDown(object? sender, ShutdownRequestedEventArgs e)
+    {
+        e.Cancel = true; // async -> need to cancel immediately
+        if (await CheckIfClosePossible())
+        {
+            Closing -= WindowIsClosing;
+            var lifetime = Application.Current?.ApplicationLifetime as IClassicDesktopStyleApplicationLifetime;
+            lifetime?.ShutdownRequested -= ApplicationIsShuttingDown;
+            lifetime?.TryShutdown();
+        }
+    }
+
+    private async Task<bool> CheckIfClosePossible()
+    {
+        var canShutdown = true;
+        if (DataContext is MainWindowViewModel mwvm)
+        {
+            if (mwvm is ICanCheckShutdown canCheck)
+            {
+                canShutdown = await canCheck.CheckIsSafeToShutdown();
+            }
+            // only checking 1 level but for this app that is OK
+            if (canShutdown && mwvm.CurrentViewModel is ICanCheckShutdown currModel)
+            {
+                try
+                {
+                    canShutdown = await currModel.CheckIsSafeToShutdown();
+                }
+                catch (Exception)
+                {
+                    canShutdown = true;
+                }
+            }
+        }
+        return canShutdown;
     }
 
     public TopLevel GetTopLevel()