Fix shell omnibox drawer layout

src/RolemasterDb.App/Components/Primitives/SurfaceDrawer.razor

@@ -2,7 +2,7 @@
 {
     <button
         type="button"
-        class="surface-drawer-backdrop"
+        class="@BuildBackdropCssClass()"
         aria-label="@CloseLabel"
         @onclick="HandleCloseAsync"></button>
 
@@ -61,6 +61,9 @@
     [Parameter]
     public string? CssClass { get; set; }
 
+    [Parameter]
+    public string? BackdropCssClass { get; set; }
+
     private string BuildCssClass()
     {
         var classes = new List<string> { "surface-drawer", $"is-{Placement.Trim().ToLowerInvariant()}" };
@@ -72,6 +75,17 @@
         return string.Join(' ', classes);
     }
 
+    private string BuildBackdropCssClass()
+    {
+        var classes = new List<string> { "surface-drawer-backdrop" };
+        if (!string.IsNullOrWhiteSpace(BackdropCssClass))
+        {
+            classes.Add(BackdropCssClass);
+        }
+
+        return string.Join(' ', classes);
+    }
+
     private Task HandleCloseAsync() =>
         OnClose.InvokeAsync();
 }