- Replace username/password with OAuth flow
- Generate PIN and open popup to app.plex.tv/auth
- Safari-compatible: open popup immediately, navigate after PIN generation
- Poll PIN status every second for authentication
- Custom loading screen in popup while generating PIN
- Plex orange button (#c87818) with icon
- Update API to accept authToken instead of credentials
- Cleanup on component unmount and popup close
- Handle popup blockers with user-friendly error messages
