Add option to switch text/background colors to black/white for better readability

Hey there!

I'm finding hard to keep reading for long periods because of the contrast white text on dark background. This is a common **readability issue** related to lots of people.

It would be great to make it **more** **accessible** for everyone by adding an option to change the colors for text and background to black and white.
Even better, would be colors like **dark gray** for text and **dull white** for background.

I love the work you did so far! And I hope it would keep improving to help everyone :)
Cheers

The issue names no files, tests, or entry points. Start by locating the interface and theme styling used for text and background colors, then clarify the intended toggle and exact palette. Done means the option is available and the resulting contrast is readable across the app.

Written by the indexing model from the issue text.