[Feature]: Bring support to DPI Toggle button as Gesture button

### 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

I can not use the DPI Toggle button as Gesture Button.

### Proposed solution

Include the DPI Toggle button in the Gesture Button selector

### Alternatives considered

_No response_

### Related area(s)

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

### Additional context

_No response_

Start by locating the GUI's Gesture Button selector and the existing DPI Toggle button action. Trace how button actions are presented and selected, then verify that DPI Toggle appears in the Gesture Button selector and can be assigned and used as a gesture.

Written by the indexing model from the issue text.