[css] Improve link contrast

Based on accessibility analysis on https://pagespeed.web.dev/analysis/https-www-michaelkelly-org/qpembick7p?form_factor=mobile

This also keeps it consistent with blog.michaelkelly.org.
Wording updates
Fix long titles on narrow screens with <wbr>
Finally add a 404 page
Tiny style tweaks, use a <main> tag, set lang
Passphraser update
Passphraser update
2 build files: mirror + deploy
Migrate to sourcehut with GH mirror
Wording and content updates; mention sourcehut
Reorder projects, link to Mastdon profile
passphraser from github.com/mjkelly/passphraser
Phassphraser update
Update projects page