[Feature]: UI scaling for HDPI screens

[95camarones]

Pre-submission Checklist

• I have searched existing issues to make sure this feature hasn't been requested

Problem Statement

The UI is very small on HDPI screens. I have tried changing GTK_DPI_SCALE, but this has no effect.

System
Linux Mint 22.1 Xia Xfce 4.18.1
6.8.0-124-generic x86_64
MacBook Pro 10,2

Proposed Solution

It would be good to be able to adjust the UI scale in the settings, or identify an environment variable that could be changed to scale the UI with Flatseal.

Alternatives Considered

No response

Additional Context

No response