v1.0.0: first stable release + launch polish

[Shaan-alpha]

Summary

First stable release (1.0). Four launch-polish items on top of the v0.9.x hardening line:

• Homepage link previews — branded Open Graph / Twitter card (app/opengraph-image.tsx + metadataBase/openGraph/twitter in layout) so sharing the site root renders a rich card.
• Autofocus the landing search (desktop, prop-gated so the results-page search doesn't steal focus).
• Inline "analyze another" search on the report page (reuses SearchBar).
• Removed unused Next starter svgs.

v1.0.0 is the code release; the public launch (domain, posts, traffic watch) is operator-run, tracked in docs/LAUNCH.md.

Test plan

• Frontend lint/tsc clean; vitest 58 passed; next build clean (/opengraph-image + /twitter-image generate)
• Backend pytest 290 passed (untouched)
• Post-merge: share the homepage URL → rich card; desktop search autofocuses; report page inline search works; mobile check