Add overall progress, notifications, and UI polish

- Unify audio/subtitle selection: single-select, auto-default,
  cross-file propagation by exact name
- Show file size in queue, group divider and reordered columns in
  track table, drop accent highlight on row selection
- Add cumulative progress bar (files finished, MB copied) to the
  stripping window
- Add Windows toast notifications on stripping completion/cancel/error
- Restart the app after settings are changed; Cancel no longer
  clears the queue, only closes the window
- Add ConfigureAwait(false) throughout MkvService so concurrent
  strips don't starve the UI thread
- Hardcode scan/strip concurrency (10/5) instead of exposing it in
  Settings

Models/JobProgressItem.cs

@@ -14,6 +14,12 @@ public class JobProgressItem : INotifyPropertyChanged
 
     public string FileName { get; set; } = string.Empty;
 
+    /// <summary>
+    /// Size of the source file in bytes, used as this job's weight when
+    /// computing overall cumulative progress across all queued files.
+    /// </summary>
+    public long FileSizeBytes { get; set; }
+
     public int Percent
     {
         get => _percent;