biomech theme: self-host Oxanium 400/700 webfont (task sa)

- Add Oxanium-Regular.woff2 and Oxanium-Bold.woff2 (latin + latin-ext
  subset, ~22 KB total) by Tyler Finck, fetched 2026-05-01 from
  https://gwfh.mranftl.com/fonts/oxanium (mirrors Google Fonts);
  released under SIL OFL 1.1.
- biomech/theme.css: add @font-face blocks pointing at the local
  files. The CSS already declared 'Oxanium' as the body font but
  the family was never loaded, so it silently fell back to system
  sans-serif. Now the geometric techy face actually renders.
- biomech/FONT_LICENSE.txt: full attribution + OFL link + source
  URL + fetch date so future maintainers can re-fetch deterministically.
- templates/embed.go: append themes/*/*.woff2 to the //go:embed glob
  (deferred from task ra because go:embed requires every pattern to
  match at least one file, which biomech now satisfies).
- README.md: append biomech entry to the bundled-fonts bullet list.

Self-hosted, no third-party CDN requests at page load; verified via
grep -RnE 'googleapis|gstatic|@import url\(http' against both source
and generated dist.

Amp-Thread-ID: https://ampcode.com/threads/T-019de000-c062-73c5-9afc-c9af422473cf
Co-authored-by: Amp <amp@ampcode.com>

0 files changed, 0 insertions, 0 deletions