refactor: consistent click behavior for volume & mic bar widgets

- left click: open audio settings panel (unchanged) - right click:
toggle mute - middle click: pwvucontrol

Modules/Bar/Widgets/Volume.qml

@@ -82,13 +82,10 @@ Item {
       settingsPanel.open(screen)
     }
     onRightClicked: {
-      pwvucontrolProcess.running = true
+      AudioService.setMuted(!AudioService.muted)
+    }
+    onMiddleClicked: {
+      Quickshell.execDetached(["pwvucontrol"]);
     }
   }
-
-  Process {
-    id: pwvucontrolProcess
-    command: ["pwvucontrol"]
-    running: false
-  }
 }