Bar widgets: modular loading refactoring via BarWidgetRegistry+NWidgetLoader

- Hot reload is working again.
- Should also be more memory efficient on multi monitors.

Modules/Bar/Widgets/MediaMini.qml

@@ -9,6 +9,10 @@ import qs.Widgets
 
 Row {
   id: root
+
+  property ShellScreen screen
+  property real scaling: ScalingService.scale(screen)
+
   anchors.verticalCenter: parent.verticalCenter
   spacing: Style.marginS * scaling
   visible: MediaService.currentPlayer !== null && MediaService.canPlay