Match Rekordbox theme to the system appearance

I would love to see a setting in Rekordbox that allows the app theme to automatically follow the system appearance.

For example, on macOS, when the system switches to Dark Mode, Rekordbox would automatically switch to the dark theme. When the system switches back to Light Mode, Rekordbox would switch back as well.

This would be especially useful for users who have macOS set to change appearance automatically based on the time of day.

A simple "System" option in the Appearance settings would make this much more convenient.

Example UI:

Appearance
- Dark
- Light
- System