Link-preview test variants

Share each URL (or paste it into opengraph.xyz / the Facebook Sharing Debugger) to compare previews.

• logo 84x36 — declares 512 (reproduces prod bug)
  https://link-preview-lab.pages.dev/logo.html
• wide 600x257
  https://link-preview-lab.pages.dev/wide.html
• square 512x512
  https://link-preview-lab.pages.dev/square.html
• banner 1200x630 (crop test)
  https://link-preview-lab.pages.dev/banner.html
• app icon 512x512
  https://link-preview-lab.pages.dev/icon.html
• OG banner 1200x630 (recommended)
  https://link-preview-lab.pages.dev/og.html