Adding masonry cover images to login page

- Added new public api: /api/Image/random-series-cover
- Updated login bg color to black
- If no cover images, use the default library background (for new installs)
- Added a cover masonry component
- updated the splash container

API/Data/Repositories/SeriesRepository.cs

@@ -116,6 +116,7 @@ public interface ISeriesRepository
     /// <returns></returns>
     Task AddSeriesModifiers(int userId, IList<SeriesDto> series);
     Task<string?> GetSeriesCoverImageAsync(int seriesId);
+    Task<string?> GetRandomSeriesCoverImageAsync();
     Task<PagedList<SeriesDto>> GetOnDeck(int userId, int libraryId, UserParams userParams, FilterDto? filter);
     Task<PagedList<SeriesDto>> GetRecentlyAdded(int libraryId, int userId, UserParams userParams, FilterDto filter);
     Task<PagedList<SeriesDto>> GetRecentlyAddedV2(int userId, UserParams userParams, FilterV2Dto filter);
@@ -183,6 +184,8 @@ public class SeriesRepository : ISeriesRepository
     private readonly Regex _yearRegex = new Regex(@"\d{4}", RegexOptions.Compiled,
         Services.Tasks.Scanner.Parser.Parser.RegexTimeout);
 
+    private static readonly Random _random = new Random();
+
     public SeriesRepository(DataContext context, IMapper mapper, UserManager<AppUser> userManager)
     {
         _context = context;
@@ -780,6 +783,19 @@ public class SeriesRepository : ISeriesRepository
             .SingleOrDefaultAsync();
     }
 
+    public async Task<string?> GetRandomSeriesCoverImageAsync()
+    {
+        var count = await _context.Series.CountAsync();
+        if (count == 0) return null;
+        
+        var skip = _random.Next(0, count);
+        
+        return await _context.Series
+            .Skip(skip)
+            .Select(s => s.CoverImage)
+            .FirstOrDefaultAsync();
+    }
+
 
     /// <summary>
     /// Returns a list of Series that were added, ordered by Created desc