The audit found these were UI-hidden but API-open — any profile (or the
anonymous default-admin) could call them directly. Added @admin_only to the 15
that mutate SHARED/global state:
- DB: update, backup, backups DELETE, restore, vacuum
- library: track DELETE, album DELETE, tracks delete-batch, clear-match
- plex clear-library; metadata-cache clear + clear-musicbrainz
- internal API keys: list, generate, revoke
Deliberately NOT gated: profile-scoped own-data ops like /api/wishlist/clear
(clears the caller's OWN wishlist via profile_id) — gating that would wrongly
block a non-admin from managing their own data. Verified by test.
Zero change for single-profile installs (the default profile IS admin), so
existing users are unaffected; only genuine non-admin profiles get 403.
Tests: non-admin → 403 on all 15 (the 403 fires before the view body, so no
destructive op runs); admin not blocked on the read-only one; wishlist/clear
stays open to non-admins (over-gating guard). 17 tests.
