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/Brightness.qml

@@ -8,13 +8,16 @@ import qs.Widgets
 Item {
   id: root
 
-  width: pill.width
-  height: pill.height
-  visible: getMonitor() !== null
+  property ShellScreen screen
+  property real scaling: ScalingService.scale(screen)
 
   // Used to avoid opening the pill on Quickshell startup
   property bool firstBrightnessReceived: false
 
+  width: pill.width
+  height: pill.height
+  visible: getMonitor() !== null
+
   function getMonitor() {
     return BrightnessService.getMonitorForScreen(screen) || null
   }