DEV: refactor to remove template overrides, add fixes

[awesomerobot]

this removes template overrides, and this theme hasn't been maintained for a while so it fixes some CSS that had regressed

removing the template overrides also allows it to work with the ai plugin topic list summary feature

Before:

After:

[CvX]

1. Are those contrasting color for visited/not visited topic links expected?
   
2. btw fyi 😅 I'll be following up this PR with a modernization changes (I get to slim down my PR after the changes in here 😃)

[awesomerobot]

1. Are those contrasting color for visited/not visited topic links expected?
   

Kind of... the original theme had used a hardcoded purple value for visited links, so I moved this to quaternary and added a color scheme to the theme (it previously had no color scheme of its own)

I guess the gap is that sites currently using the theme won't automatically get switched to its own color scheme? and they end up with the default value for quaternary, which is red 🤔

[awesomerobot]

Instead of the color palette I've moved the visited link color to a variable, this will avoid sites updating the theme ending up in a state with red as the visited link color