- Add passkey login as alternative authentication method
- Support multiple passkeys per user with custom names
- Backend: WebAuthn service, auth strategy pattern, API endpoints
- Frontend: passkey management UI in settings, login option
- Fix: convert downloader check from sync requests to async httpx
to prevent blocking the event loop when downloader unavailable
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>