feat: add grid/list view toggle to track gallery with hover-reveal art cards

DeepDrftPublic.Client/Pages/TracksView.razor.cs

@@ -1,4 +1,5 @@
 using DeepDrftModels.DTOs;
+using DeepDrftPublic.Client.Controls;
 using DeepDrftPublic.Client.Services;
 using DeepDrftPublic.Client.ViewModels;
 using Microsoft.AspNetCore.Components;
@@ -17,6 +18,9 @@ public partial class TracksView : ComponentBase, IDisposable
     private IStreamingPlayerService? _subscribedService;
     private PersistingComponentStateSubscription _persistingSubscription;
 
+    // Ephemeral view-mode selection — presentation-only, not persisted across navigation.
+    private GalleryViewMode _viewMode = GalleryViewMode.Grid;
+
     protected override async Task OnInitializedAsync()
     {
         // Carry the prerendered page across the prerender -> interactive (WASM) seam.