Mirror the rethink Gitea theme (data-theme=rethink) on the docs site:
- docs/stylesheets/extra.css maps the exact palette onto Material's slate
scheme: body #0a0f1f, nav #061541, text #eef1f6, primary #569bcc,
accent #55bbff, borders #294274; square corners and blue card/table
borders echoing the Gitea repo panels.
- Force dark-only (drop the light/dark toggle; Gitea is dark-only).
- Rename site to lowercase 'a rethink development' (site_name, copyright,
landing H1).
Verified: mkdocs build --strict clean; rendered landing + content pages
in-browser against the live Gitea page — colors, header bar, links, and
cards match.
Signed-off-by: disqualifier <dev@disqualifier.me>
