Title: Power panel never opens on battery-less desktops (self-closes immediately, QML binding loop)

## What happened
On a desktop system with no battery (Bosgame M5, AXB35-02 board — no UPower battery device present), the Power panel (`omarchy.power`, bound to SUPER+CTRL+P by default) never actually displays. Triggering it via keybind, the bar widget, or `omarchy-shell shell toggle omarchy.power` all silently no-op — the panel opens and instantly closes itself in the same frame.

The shell log shows:
```
WARN scene: QML Panel at file:///usr/share/omarchy/shell/plugins/panels/power/Panel.qml[9:1]: Binding loop detected for property "opened":
WARN scene: QML IpcHandler at .../Panel.qml[177:3]: Handler was registered but will not be used because another handler is registered for target omarchy.power
```

## What was expected
The Power panel (suspend/lock/shutdown/power-profile controls) should open normally on any machine, since none of those actions require a battery to be present. Only the battery-specific sub-section should reasonably depend on `batteryPresent`.

## Root cause
In `shell/plugins/panels/power/Panel.qml`:

```qml
onOpenedChanged: {
  if (opened) {
    if (!batteryPresent) {
      close()
      return
    }
    ...
  }
}

onBatteryPresentChanged: if (!batteryPresent) close()

visible: batteryPresent
implicitWidth: batteryPresent ? button.implicitWidth : 0
```

The whole panel's `visible` and `implicitWidth` are gated on `batteryPresent` at the component root, and `onOpenedChanged` force-closes the panel immediately if there's no battery. On a battery-less desktop `batteryPresent` is always `false`, so the panel opens and self-closes in the same tick every time — which is what triggers the QML binding-loop warning above. There's already a correctly-scoped battery gate further down (`open: root.opened && root.batteryPresent` on the battery-info sub-section), so the fix is just removing the over-broad gate at the root.

## Steps to reproduce
1. On a desktop with no UPower battery device (any headless/desktop Strix Halo mini PC, or any desktop build)
2. Press SUPER+CTRL+P (or trigger `omarchy-shell shell toggle omarchy.power`)
3. Nothing appears; shell log shows the binding-loop warning above

## System details
- Omarchy: 4.0.1-1
- Hyprland: 0.56.2
- Kernel: 7.1.9-arch1-2
- Machine: Bosgame M5 (Mobo: AXB35-02), AMD Ryzen AI Max+ 395 / Radeon 8060S
- No system battery present (UPower reports no display device)

## Suggested fix
Remove the `if (!batteryPresent) { close(); return }` block from `onOpenedChanged`, remove `onBatteryPresentChanged: if (!batteryPresent) close()`, and drop the `batteryPresent` condition from the root `visible`/`implicitWidth` bindings — leave the existing, correctly-scoped `open: root.opened && root.batteryPresent` on the battery sub-section as the only battery gate. Happy to open a PR with this fix if useful.