feat(ags-v3): desktop adaptation — ultrawide scaling, brain power panel, system stats

- Scaling 16px base pour ultrawide 3440x1440
- Bar: CPU/RAM/GPU visible, media single player (skip playerctld), network tooltip LAN/WAN IPv4
- Volume: class module pour sizing cohérent
- Battery: désactivé (PC fixe)
- Clock: tooltip calendrier + uptime
- BrainPower: panel enrichi (focus, session, intentions, todos, repos git, derniers commits)
- App: BrainPower sur moniteur principal uniquement
- Heartbeat: Layer.TOP pour compatibilité COSMIC

ags-v3/widget/Heartbeat.tsx

@@ -11,7 +11,7 @@ export default function Heartbeat(gdkmonitor: Gdk.Monitor) {
       exclusivity={Astal.Exclusivity.NONE}
       anchor={TOP | LEFT | RIGHT}
       application={app}
-      layer={Astal.Layer.OVERLAY}
+      layer={Astal.Layer.TOP}
     >
       <eventbox
         onHover={() => {