Add Custom refresh rate feature

[DDOneApps]

closes #355
This implementation is Vibe-coded, but i did testing and everything worked on my pixel 9a.
The implementation is similar to other features.

[sameerasw]

Thanks a lot for the feature!

I think there's some improvements and disclaimers which can be added but already working nicely!

[DDOneApps]

Thank you for merging my pr. I forgot to exclude the Codex analysis notes
That i let codex make to understand structure and implementation of the app. If you want you can leave it for other AIs to understand,but i think you don’t need it anymore.

[sameerasw]

Ohhh I missed that, I am going to remove it for now but I don't mind having documentation but maybe in a separate dir or so :)