feat(seo): redesign the Open Graph images

The old previews showed an outdated UI and still listed Maven and five
registries. The new set shares one layout: headline on the left, a card
with real pkgdiff data on the right, the four registries in the footer.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: Enes Yağız