fix(mobile): reset video controls hide timer when showing controls changes

The hide timer currently only resets when the status of the video
changes, but does not account for when the controls change. This means
that two things happen:

 1. The hide timer does not reset when the controls become visible
    again, the controls will stay visible forever or until the playback
    status changes.
 2. The hide timer will fire too quickly, and will hide the controls
    much sooner than 5 seconds if the controls are hidden and then shown
    again before the hide timer fires.

mobile/lib/widgets/asset_viewer/video_controls.dart

@@ -60,6 +60,9 @@ class VideoControls extends HookConsumerWidget {
       }
     });
 
+    ref.listen(assetViewerProvider.select((v) => v.showingControls), (prev, showing) {
+      if (showing && prev != showing) hideTimer.reset();
+    });
     ref.listen(provider.select((v) => v.status), (_, __) => hideTimer.reset());
 
     final notifier = ref.read(provider.notifier);