refactor(bar): modularize bar widgets and layout

modules/bar/BatteryIndicator.qml

@@ -0,0 +1,11 @@
+pragma ComponentBehavior: Bound
+
+import qs.ui
+import qs.services
+
+BarButton {
+  hoverHighlight: false
+  pointerCursor: false
+  label: `${Battery.percentage}% ${Battery.energyRate}W`
+  iconSource: Battery.icon
+}