- Remove top border-radius from AuthCard (flat top edge, rounded bottom)
- Add overflow-hidden so rainbow gradient bar stays within card bounds
- Remove rounded-t-2xl from gradient bar (no longer needed)
- Increase AuthDivider vertical margin from my-5 to my-8
- Update test selector to match new rounded-b-2xl class
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>