Migrate and Backups detached their sub-tab strip from the content (16px gap)
and Backups had no top-level header and a transparent (card-less) body — so
both read as different from the per-app Config sub-tabs.
- Migrate: nest .tabs-content inside the same .tabs-wrapper as .tabs-list (the
canonical app-detail structure) and drop the gap, so the strip joins the
content card with no space and clean corners.
- Backups: inject the shared "Backups" .config-title header above the embedded
BackupPage; drop the sub-tab strip's bottom gap; give the content (.main) the
connected .tabs-content surface (card bg + rounded bottom) and round the
strip's outer top corners — so it reads as one tabs-within-tabs unit.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>