Add capability-first account and calendar setup flow

Wino.Mail.WinUI/Views/ProviderSelectionPage.xaml.cs

@@ -12,6 +12,16 @@ public sealed partial class ProviderSelectionPage : ProviderSelectionPageAbstrac
 
     private void ProviderSelectionChanged(ItemsView sender, ItemsViewSelectionChangedEventArgs args)
     {
+        if (sender.SelectedItem == null) return;
+
         ViewModel.SelectedProvider = sender.SelectedItem as Wino.Core.Domain.Interfaces.IProviderDetail;
     }
+
+    private void AccountColorGridView_SelectionChanged(object sender, SelectionChangedEventArgs e)
+    {
+        if (e.AddedItems.Count > 0)
+        {
+            AccountColorFlyout.Hide();
+        }
+    }
 }