Show if a track is completed on overview page

On the tracks page, it would be nice to visually be able to see if a track has been completed. Yes, you can see that via the # exercises completed/# exercises text, but a visual indication might be nice.


Start at the tracks page and inspect how the overview renders each track and its exercises-completed count. Done means a completed track has a clear visual indication in addition to the existing count, with the incomplete state still understandable.

Written by the indexing model from the issue text.