New 5th Overview tab 'Migrate' with a nested segmented sub-tab row reusing the
per-app Config-tab .tabs-list/.tab-button design:
- Restore: a standalone MigratePage (cross-host migrate moved out of BackupPage
into its own controller + fragment + modal; own data fetch + task dispatch).
- Peers: reuses the existing PeersPage (container-parameterized) + its template.
Both lazy-loaded on first open and disposed on apps-feature unmount. Additive —
migrate is still in the backup center and Peers still in Admin until the next
commits remove the duplicates.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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