- Restore empty-state 'Open Locations' now deep-links to the backup center's
Locations sub-tab: the embedded center honors /overview/backups/<sub> and
switchTab()s to it after mount (was landing on Dashboard).
- PeersPage.notify + MigratePage.notify use the real window.notificationSystem
(were calling a never-defined window.showNotification → console-only).
- Remove the now-dead Admin config-manager peers branch (Peers left Admin).
- Trim the dead migrate.json/peers fetch + hostnameToPeerName from BackupPage
(no consumer after the migrate removal).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>