chore: add HF Spaces deployment config and fix frontend API URL

Fix: Overhaul Facebook post detection to filtered comments using [role='feed'] strategy and improve button positioning

feat: oEmbed scraping for Facebook/X URLs, remove social URL blocks

fix(frontend): block social URL preview + better error card for social URLs

fix: cold start 502, favicon, verify state persistence

feat(frontend): apply frontend-design, web-design-guidelines, architect-review skills