Restyles every template with a hand-written dark Gitea-style theme
(web/static/app.css, ~270 lines: badges, buttons, cards, focus rings,
prefers-reduced-motion) and completes the htmx polling wiring for all
four dashboard cards. Adds the repeatable setup-web-linux.sh installer
(idempotent: pip install '[web]' non-editable, render ci-web.service,
template [web]/[web.oidc] into config.toml, prompt for keyring secrets,
print Gitea OIDC registration steps, enable/restart the unit) plus
deploy/systemd/ci-web.service and docs/WEB-UI.md.
