Nested LiveView that renders the notifications bell in the global layout.

Embedded from layout_wrapper.ex via live_render/3 with sticky: true so it keeps its socket across page navigations and its own PubSub subscription stays live. It owns its handle_info callbacks for {:notification_created, _} / {:notification_seen, _} / {:notification_dismissed, _} / {:notifications_bulk_updated, _}, refreshing the badge count and dropdown contents on each event.

Not routable on its own — mount expects user_uuid in the nested session.