Dock: Support mouse wheel gestures on dock items

### Description of the new feature / enhancement

It would be useful if dock items could react to mouse wheel input and execute commands on wheel up / wheel down.

This could enable scenarios such as:
- Volume up / down
- Switching between tracks or apps/sessions in Media Controls

This would make dock items more interactive and allow compact controls without requiring extra buttons or opening additional UI.

### Scenario when this would be used?

UX

### Supporting information

_No response_

Start by locating the dock-item input handling and command-dispatch entry points in PowerToys; the issue names no files or tests. Clarify how wheel-up and wheel-down actions should be configured and which dock items support them. Done means dock items can receive both wheel directions and execute the corresponding commands.

Written by the indexing model from the issue text.