feat: add search/album/genre filtering and /albums + /genres browse pages

DeepDrftModels/DTOs/AlbumSummaryDto.cs

@@ -0,0 +1,14 @@
+namespace DeepDrftModels.DTOs;
+
+/// <summary>
+/// One distinct album with its track count and a representative cover image key. Backs the
+/// /albums browse grid.
+/// </summary>
+public class AlbumSummaryDto
+{
+    public required string Album { get; set; }
+    public int TrackCount { get; set; }
+
+    /// <summary>ImagePath of the first track in the album that has one; null when none do.</summary>
+    public string? CoverImageKey { get; set; }
+}