Shared voxvera.org links now render a real image card, not just a text
summary. Adds site/og-card.jpg (1200x630, ~90KB, derived from the
"say something… voxvera.org" custom art) and wires og:image +
twitter:image + image dimensions/alt on the home, board, and safety
pages, bumping twitter:card to summary_large_image.
Per-flyer previews remain out of scope (fragment URLs are invisible to
servers; this stays a purely static site). Test asserts all three pages
declare the og:image and that the asset is served as JPEG. Full suite
378 passing.
Co-Authored-By: Claude Opus 4.8 <[email protected]>
