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/QueuedFileItem.cs

@@ -32,6 +32,7 @@ public class QueuedFileItem : INotifyPropertyChanged
 
     public string FilePath { get; }
     public string FileName => Path.GetFileName(FilePath);
+    public string FileSizeDisplay { get; }
     public ObservableCollection<TrackItem> Tracks { get; } = new();
 
     public string Status
@@ -76,9 +77,33 @@ public class QueuedFileItem : INotifyPropertyChanged
     public QueuedFileItem(string filePath)
     {
         FilePath = filePath;
+        FileSizeDisplay = FormatFileSize(filePath);
         Tracks.CollectionChanged += OnTracksChanged;
     }
 
+    private static string FormatFileSize(string filePath)
+    {
+        try
+        {
+            long bytes = new FileInfo(filePath).Length;
+            string[] units = { "B", "KB", "MB", "GB", "TB" };
+            double size = bytes;
+            int unitIndex = 0;
+            while (size >= 1024 && unitIndex < units.Length - 1)
+            {
+                size /= 1024;
+                unitIndex++;
+            }
+            return unitIndex == 0
+                ? $"{size:0} {units[unitIndex]}"
+                : $"{size:0.#} {units[unitIndex]}";
+        }
+        catch
+        {
+            return string.Empty;
+        }
+    }
+
     private void OnTracksChanged(object? sender, NotifyCollectionChangedEventArgs e)
     {
         if (e.NewItems != null)