Appearance style selection only works once

[largestgithubuseronearth]

Describe the bug
If you change your color style (Dark, Dark blue) then you can't change it back until you close the preferences dialog.

To Reproduce
Steps to reproduce the behavior:

1. Open Preferences -> Appearance.
2. Select the other style than your current one.
3. Now both options appear selected and you can't change back anymore.
4. It will remain this way until you close and reopen the Preferences dialog.

Expected behavior
When you select one option, the others would be deselected. You would be able to click back and forth to get a quick preview of the style without having to close the dialog.

Screenshots

Screencast.From.2026-02-18.08-14-10.webm

Desktop (please complete the following information):

• Fedora Silverblue 43, GNOME 49
• Planify 4.18.0, Flathub

Additional context
#2276 is probably the same as this but the author of that issue didn't include any useful info.