Page modals: cleaner behaviour and refreshed copy

The slide-over and confirmation modals across the page management flow got a round of polish:

• Dismiss on escape. Hitting Esc closes the modal, as you would expect.
• Focus the first input. When a modal opens, focus lands on the first interactive element so you can start typing immediately.
• Restore focus on close. When the modal closes, focus returns to the element that opened it — important for keyboard navigation and for screen readers.
• Outside click behaves. Clicking outside a confirmation modal no longer dismisses pending changes silently; you get a "discard changes?" prompt.

The i18n strings around these modals also got a careful pass — clearer labels, gentler tone, less software-engineer-ese.