fix(mobile): fix stale refs in use timer

The timer hook preserved the values of the original local variables,
which caused issues when hiding controls for videos. The callback can be
changed so that it always sees the latest value with useRef, and it can
be simplified significantly using a function rather than state class.

mobile/lib/presentation/widgets/asset_viewer/bottom_bar.widget.dart

@@ -74,7 +74,7 @@ class ViewerBottomBar extends ConsumerWidget {
                   child: Column(
                     mainAxisSize: MainAxisSize.min,
                     children: [
-                      if (asset.isVideo) VideoControls(key: ValueKey(asset.heroTag), videoPlayerName: asset.heroTag),
+                      if (asset.isVideo) VideoControls(videoPlayerName: asset.heroTag),
                       if (!isReadonlyModeEnabled)
                         Row(mainAxisAlignment: MainAxisAlignment.spaceEvenly, children: actions),
                     ],