Some UI changes on settings.

Wino.Mail.WinUI/Views/Calendar/CalendarEventComposePage.xaml

@@ -63,7 +63,9 @@
                             HorizontalContentAlignment="Left"
                             Style="{StaticResource DefaultButtonStyle}">
                             <Button.Flyout>
-                                <Flyout Placement="BottomEdgeAlignedLeft">
+                                <Flyout
+                                    x:Name="CalendarSelectionFlyout"
+                                    Placement="BottomEdgeAlignedLeft">
                                     <ScrollViewer MaxHeight="360">
                                         <ItemsControl ItemsSource="{x:Bind ViewModel.AvailableCalendarGroups, Mode=OneWay}">
                                             <ItemsControl.ItemTemplate>

Wino.Mail.WinUI/Views/Calendar/CalendarEventComposePage.xaml.cs

@@ -155,6 +155,7 @@ public sealed partial class CalendarEventComposePage : CalendarEventComposePageA
         if (e.ClickedItem is AccountCalendarViewModel calendar)
         {
             ViewModel.SelectedCalendar = calendar;
+            CalendarSelectionFlyout.Hide();
         }
     }