- Add LINGUIST role to UserRole enum (backend + frontend)
- Grant linguists access to QC Review, Final Review, review notes, and VTT editing
- Add MongoDB migration to update schema validator with linguist role
- Add admin seed: vadymsamoilenko@oliver.agency is promoted to admin on startup
- Add User Management sidebar link for admin users
- Fix Login.tsx role type cast to use UserRole instead of hardcoded union
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
