Share card QA

Every page's Open Graph card, rendered in WhatsApp and LinkedIn chrome at true proportions, so a card can be judged before a link is ever pasted into a chat. WhatsApp is where these booking links actually travel, so its bubble is the one to trust.

Data is scanned from the built HTML by scripts/build-og-preview.py. 301 redirect stubs are excluded from scoring. Default card in use: 1200×630 JPEG, 58 KB.