[Feature]: Show battery level on tray icon

### Pre-flight checklist

- [x] I searched existing issues and the [Roadmap](https://github.com/AprilNEA/OpenLogi#roadmap), and this isn't already tracked.

### Problem / motivation

In the offical G Hub driver, users can quickly see their mouse's battery level in context menu, like the screenshot below:

However, now I can't find the same or similar feature in OpenLogi.

### Proposed solution

If it possible, I hope OpenLogi's tray icon can provide the same feature, show my battery level and predicted using time (if possible) in tray icon. Maybe not show a progress bar but show one line of text like `PRO Wireless: 50%`, or `PRO Wireless 50%, eta:x hr xx min`

If needed, I can help to test and write some parts of this feature on Windows. Thanks to consider.

### Alternatives considered

I've considered some way to this feature, including but not limited to below:

- Show a battery percentage number on tray icon's right button menu like the offical G Hub driver
- Show battery percentage as icon on tray icon
- Show a level bar as icon on tray icon
- Show level text in context menu

Below is some inspiration I drew in Figma that you can reference:

### Related area(s)

- [x] GUI
- [ ] CLI
- [ ] Button actions / remapping
- [ ] DPI
- [ ] SmartShift
- [ ] Per-application profiles
- [ ] Configuration (TOML)
- [ ] Auto-update
- [ ] Other

### Additional context

_No response_

No file or test is named. Start by tracing the GUI tray-icon entry point and how OpenLogi exposes the mouse battery state, then compare the requested percentage and context-menu presentation with existing GUI behavior. Done means the tray interface presents the battery level in an agreed format, with predicted usage time only if the project can support it.

Written by the indexing model from the issue text.