feat: add seating plans for learning groups

LehrerApp.Desktop/Views/Groups/SeatingPlanDialog.axaml.cs

@@ -0,0 +1,19 @@
+using Avalonia.Controls;
+using Avalonia.Interactivity;
+using LehrerApp.Desktop.ViewModels.Groups;
+
+namespace LehrerApp.Desktop.Views.Groups;
+
+public partial class SeatingPlanDialog : Window
+{
+    public SeatingPlanDialog() => InitializeComponent();
+
+    private void OnSave(object? sender, RoutedEventArgs e)
+    {
+        if (DataContext is not SeatingPlanDialogViewModel vm) return;
+        vm.SaveCommand.Execute(null);
+        if (vm.Result is not null) Close(true);
+    }
+
+    private void OnCancel(object? sender, RoutedEventArgs e) => Close(false);
+}