Fixes Milestones progress bar statuses not rendered correctly after Gitea
1.23.x update. Adds explicit styling for progress bars, using theme colours.
Fixes#133
In the latest releases, Gitea has fixed a lot of the styling issues we
had manually fixed in the past.
Additionally, the recent style adjustments they did look a lot better
so it is better to remove our custom styling as much as possible, and
follow stock Gitea. Making it easier to upgrade in the future.
* Fix broken styling
* Remove custom font
* Cleanup unused variables
* Add code comments
