Lineup menus offered Move to page and Copy to page with every page listed,
unlike every other placed item. They now get the same "Copy to next page"
and "Copy to previous page" items, in the same place and with the same
toasts. A copied lineup and its spots get ids that carry the originals'
(page_copy_id.dart), so a page that already has the lineup, or a copy of
it, is not offered and gets no other, locally and on cloud.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>