CavaService improvements

- bring back autosens for better visualization at  low volume input
- enable Cava process as long as we have a visualizer and the sidePanel
is open, this helps capture audio when there is no active mpris player
(ex: mpv, game audio, etc...)

shell.qml

@@ -63,6 +63,9 @@ ShellRoot {
   IPCManager {}
 
   Component.onCompleted: {
+    // Save a ref. to our sidePanel so we can access it from services
+    PanelService.sidePanel = sidePanel
+
     // Ensure our singleton is created as soon as possible so we start fetching weather asap
     LocationService.init()
   }