[Bug]: Thumbwheel set to control volume ignores sensitivity

### Pre-flight checklist

- [x] I searched [existing issues](https://github.com/AprilNEA/OpenLogi/issues?q=is%3Aissue) and this is not a duplicate.
- [x] I am on the [latest release](https://github.com/AprilNEA/OpenLogi/releases/latest) or a recent `master` build.
- [x] I quit **Logi Options+** before running OpenLogi (the two apps fight over HID++ access and only one can own a receiver at a time).

### Which part of OpenLogi?

GUI (desktop app)

### OpenLogi version

0.7.10

### Operating system

Windows

### OS version & architecture

11, x86_64

### Device model

MX Master 3s

### How is the device connected?

Logi Bolt receiver

### Affected area(s)

- [ ] Device discovery / detection
- [x] Button remapping
- [ ] DPI control
- [ ] SmartShift
- [ ] Per-application profiles
- [ ] Battery status
- [x] Settings / configuration (TOML)
- [ ] Auto-update
- [ ] Menu bar / tray
- [ ] Other

### What happened?

I have set the thumbwheel to control the volume, and no matter how much I set the sensitivity of the thumbwheel later, the volume only goes up or down by 2. I would like to at least reduce/increase a quarter of the volume in just one swipe and I expected that I could adjust that with that setting.

### Steps to reproduce

1. Bind the thumbwheel to Volume Up / Down
2. Go to "Pointer" settings tab and adjust the sensitivity

### Diagnostics report

```markdown

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### `openlogi list` output

```text

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### Logs

```shell

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### macOS permissions (if applicable)

- [ ] OpenLogi has **Accessibility** permission (needed to remap buttons via the event tap).
- [ ] OpenLogi has **Input Monitoring** permission (needed for Bluetooth-direct devices and capture).

Start in the desktop GUI's Pointer settings and follow how thumbwheel sensitivity is applied when the wheel is bound to Volume Up / Down. Reproduce on Windows with an MX Master 3s, then verify that changing sensitivity changes the volume increment rather than leaving it fixed at 2.

Written by the indexing model from the issue text.