Address reviewer follow-ups: powerProfile detect, slider live-value, glyphs

- powerProfile now hides on machines without power-profiles-daemon by
  checking against the published profile set rather than a never-undefined
  enum, and uses mdi-scale-balance for Balanced (not battery-charging).
- networkPanel renames the QML-keyword-shadowing 'signal' property to
  'signalStrength'; ethernet glyph corrected to mdi-ethernet (not the
  access-point icon).
- workspacesPro indicator color guards against null bar during construction.
- Common.Slider keeps an internal liveValue so external value bindings
  survive a drag; sliders fed from PipeWire/brightnessctl now follow
  external changes after the user interacts.
- audioPanel drops the redundant default-sink PwObjectTracker since the
  candidate-sinks tracker already covers it.
- networkPanel guards scan/connect commands against re-entry while the
  previous Process is running.
- notificationCenter only instantiates its NotificationServer when the
  module is opted in via settings.replaceMako (default off) so it does
  not collide with mako out of the box.
- PopupCard fully opaque while open (previously 0.98) — removes a
  visible ghost outline on first render.
- Drop dead code: calendar trailing MouseArea, weatherFlyout's unused
  parseForecast/forecast property, idleInhibitor's holdSeconds,
  media's scrollAnim.position; gate media's scroll animation off in
  vertical bar mode.

default/quickshell/bar/common/PopupCard.qml

@@ -77,7 +77,7 @@ PopupWindow {
     border.color: root.bar ? root.bar.foreground : "#cacccc"
     border.width: 1
     radius: 0
-    opacity: root.open ? 0.98 : 0
+    opacity: root.open ? 1.0 : 0
 
     Behavior on opacity {
       NumberAnimation { duration: 140; easing.type: Easing.OutCubic }