Add System/Light/Dark preference for iPhone and iPad, restore the iPad
sidebar brand mark, ship a DEBUG seed-demo URL for rich placeholder data,
and refresh GitHub Pages with the device composite, full-bleed pale-green
hero wash, and transparent Mac screenshot chrome.
Capture Mac and iPhone product shots for zh/en × light/dark, store under
assets/screenshots/{lang}/{theme}/, and swap images when the page
toggles language or appearance (including system theme).
Add optional StoreKit support tip (features stay free), redesign the
landing page with zh/en + light/dark and product shots, and ship
iPhone/iPad/Mac App Store screenshot sets.
Rocky