Fix: consistent check/revert order + enable accept buttons

All three element sections (webcam border, countdown, web URI) now use
consistent [✕][✓] button order. Green check buttons enabled with click
handlers that save current values as snapshot baseline — revert undoes
to last accepted state, not initial selection.

Countdown section buttons were swapped (had [✓][✕], now [✕][✓]).
Webcam and web sections already had correct visual order.

1e of 7-issue polish batch. 207 tests, 0 warnings.

MainWindow.xaml.cs

@@ -572,15 +572,36 @@ public partial class MainWindow : Window
         }
     }
 
+    private void WebcamBorderAccept_Click(object sender, RoutedEventArgs e)
+    {
+        if (_snapshotElement is Models.Source src)
+        {
+            _snapshotBorderColor = src.BorderColor;
+            _snapshotBorderWidth = src.BorderWidth;
+        }
+    }
+
     private void CountdownRevert_Click(object sender, RoutedEventArgs e)
     {
         if (_snapshotElement is Models.Source src)
             src.TimerMinutes = _snapshotTimerMinutes;
     }
 
+    private void CountdownAccept_Click(object sender, RoutedEventArgs e)
+    {
+        if (_snapshotElement is Models.Source src)
+            _snapshotTimerMinutes = src.TimerMinutes;
+    }
+
     private void WebRevert_Click(object sender, RoutedEventArgs e)
     {
         if (_snapshotElement is Models.Source src)
             src.WebUri = _snapshotWebUri;
     }
+
+    private void WebAccept_Click(object sender, RoutedEventArgs e)
+    {
+        if (_snapshotElement is Models.Source src)
+            _snapshotWebUri = src.WebUri;
+    }
 }