Address momus review: fix icons, vertical layout, popup coordination

- Replace nerd font glyphs that were stripped during the initial widget
  writes with verified codepoints sourced from the JetBrains Mono Nerd
  Font cmap (cpu-64-bit, scale-balance, notification-clear-all, etc).
- systemStats now switches to a Column layout when the bar is vertical
  so the widget no longer overflows a 28px-wide side bar.
- Remove notificationCenter from defaults: it registers a notification
  server and would collide with the mako daemon Omarchy autostarts.
- PopupCard owns the popout coordinator lifecycle and delegates close to
  its widget owner when provided; calendar and media now pass owner.
- brightness debounces brightnessctl writes through a coalescing timer
  to avoid spawning a process per slider tick.
- audioPanel tracks unfiltered Pipewire sinks/streams via PwObjectTracker
  so audio metadata becomes available before filtering.
- ModuleSlot re-injects bar/moduleName/settings whenever the bar config
  serial changes so widget settings update live with bar.json.
- Guard null bar references in workspacesPro and systemStats components
  that are constructed before bar injection.

default/quickshell/bar/widgets/networkPanel.qml

@@ -149,7 +149,7 @@ Item {
         }
 
         Common.PillButton {
-          iconText: ""
+          iconText: "󰑐"
           foreground: root.bar.foreground
           horizontalPadding: 8
           verticalPadding: 4
@@ -205,7 +205,7 @@ Item {
 
       Common.PillButton {
         width: parent.width
-        iconText: ""
+        iconText: "󰖩"
         text: "Open Wi-Fi manager"
         foreground: root.bar.foreground
         horizontalPadding: 10