Missing theming on repositories pages

HTML pages served from debusine.web.archives are missing most theming: see https://deb.debusine.debian.net/debian/r-cjwatson-debusine/ for an example. Can we do better here?

It's OK if it's too hard to share the theme selection between domains, but I'd at least like most of the usual CSS to be applied, with a centred footer and so on, and ideally at least part of the top navigation bar.