Replace CSS-only modal-open class toggle with a shared useScrollLock
hook that uses position:fixed + scroll position save/restore. This
reliably prevents background scrolling on all browsers including
iOS Safari.
The hook supports nesting (lock counter) so stacked modals (e.g.
MedDetail → RefillModal) work correctly.
Also adds missing modal states to the scroll lock: showRefillModal,
showEditStockModal, showImageLightbox, scheduleLightboxImage.
Replaces the inline 40-line scroll lock in MobileEditModal with the
shared hook.
Daniel Volz
2aa6b1f406