Shared links didn't unfurl in Messenger: robots.txt disallowed /watch/ for ALL
user-agents, so facebookexternalhit honoured it and got a blocked (403) fetch —
the OG tags were correct but never read. Add an allow group for the link-preview
bots (facebookexternalhit, Twitterbot, Discordbot, WhatsApp, Slack, Telegram,
LinkedIn, …) so they can fetch share pages; the wildcard still keeps /watch/ out
of search indexes. Release v0.32.1.
The public landing had no meta description and no robots.txt (the SPA fallback
returned index.html for /robots.txt, so crawlers saw an invalid file). Add a
description + basic OG tags to index.html and a real robots.txt that allows the
landing but disallows the API/auth/watch surfaces. Lighthouse (dev): SEO 83->100.
