Override Background mapper to preserve UIToolbar native system appearance

Co-authored-by: haavamoa <2527084+haavamoa@users.noreply.github.com>

Author: Copilot

src/library/DIPS.Mobile.UI/Components/Toolbar/ToolbarHandler.cs

@@ -10,6 +10,10 @@ public ToolbarHandler() : base(PropertyMapper)
         new PropertyMapper<Toolbar, ToolbarHandler>(ViewMapper)
         {
             [nameof(Toolbar.Buttons)] = MapButtons,
+            // Prevent MAUI from overriding the native platform view's own background rendering.
+            // On iOS, UIToolbar manages its own system appearance (blur/Liquid Glass);
+            // on Android, we set the background explicitly in CreatePlatformView.
+            ["Background"] = static (_, _) => { },
         };
 
     private static partial void MapButtons(ToolbarHandler handler, Toolbar toolbar);