[Feature]: Affect gesture in top button of MX Vertical

### 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 want use the top button of my MX Vertical mouse with Gesture function unless one of side button. Is that possible ?

### Proposed solution

Configure top button with Gesture function.

### Alternatives considered

_No response_

### Related area(s)

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

### Additional context

_No response_

Start by reviewing the button actions/remapping implementation and how Gesture is currently assigned to side buttons. Confirm the supported MX Vertical button capabilities and existing configuration path; done means the top button can be configured with Gesture in the same way as a side button.

Written by the indexing model from the issue text.