Allow requests to be cancelled.

Make workers have a CancellationTokenSource

API/Workers/PeriodicWorkers/UpdateChaptersDownloadedWorker.cs

@@ -8,12 +8,12 @@ public class UpdateChaptersDownloadedWorker(TimeSpan? interval = null, IEnumerab
 {
     public DateTime LastExecution { get; set; } = DateTime.UnixEpoch;
     public TimeSpan Interval { get; set; } = interval??TimeSpan.FromMinutes(60);
-    protected override BaseWorker[] DoWorkInternal()
+    protected override async Task<BaseWorker[]> DoWorkInternal()
     {
         foreach (Chapter dbContextChapter in DbContext.Chapters.Include(c => c.ParentManga))
             dbContextChapter.Downloaded = dbContextChapter.CheckDownloaded();
 
-        DbContext.Sync();
+        await DbContext.Sync(CancellationTokenSource.Token);
         return [];
     }
 }