fix: rewrite TopTags query to avoid EF Core collection navigation translation error

Lactose/Repositories/StatsRepository.cs

@@ -62,11 +62,14 @@ public class StatsRepository(LactoseDbContext context) : IStatsRepository {
         dto.PublicAssets = context.Assets.Count(a => a.DeletedAt == null && a.IsPubliclyShared);
         dto.PrivateAssets = context.Assets.Count(a => a.DeletedAt == null && !a.IsPubliclyShared);
 
-        dto.TopTags = context.Tags
-            .Select(t => new TagStatDto {
-                Id = t.Id,
-                Name = t.Name,
-                AssetCount = t.Assets != null ? t.Assets.Count(a => a.DeletedAt == null) : 0
+        dto.TopTags = context.Assets
+            .Where(a => a.DeletedAt == null)
+            .SelectMany(a => a.Tags)
+            .GroupBy(t => new { t.Id, t.Name })
+            .Select(g => new TagStatDto {
+                Id = g.Key.Id,
+                Name = g.Key.Name,
+                AssetCount = g.Count()
             })
             .OrderByDescending(t => t.AssetCount)
             .Take(10)