fix(ui): replace native confirm()/alert() with shared dialogs and toasts
New app-confirm-dialog (wraps existing app-dialog + app-button) replaces
every native confirm() across media library bulk-delete, static pages
editor (delete/bulk-delete), builder save-bar (publish/reset-draft),
project-editor-page (reset-section), homepage/languages/widgets sections
(remove block/language/widget), and cart (clear-cart).
Cart's native alert() calls (delivery/terms validation, email send
success/failure) now route through the existing UserNotificationService
toast pipeline instead.
No native confirm()/alert()/prompt() remain in production UI.
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