feat: Add Duo Security card to /admin/sync overview + detail page
- Added Duo card to sync overview grid (category: 2FA/MFA, green)
- Shows accounts, users, phones, auth logs counts + bypass/disabled warning
- Created /admin/sync/duo detail page with:
- Stat cards (accounts, users, phones, auth logs, groups, integrations)
- Parent account summary
- Child accounts table with user counts, matched company, sync time
- Sync Now button with polling for completion
- Created GET /api/duo/status endpoint (counts + last sync + bypass count)
- Added duo.ico logo