iOS Safari has no Element.requestFullscreen (fullscreen is video-only),
so tapping the map band or 'View on map' silently did nothing on
iPhones. Fall back to a fixed-position CSS overlay driven by state when
the Fullscreen API is missing or its promise rejects, locking body
scroll while open. The Leaflet map already re-measures via the shared
isFullscreen flag. New e2e journey simulates the iOS condition by
deleting the API and asserts the overlay opens and closes; it fails
against the current production build.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
