- Full setup form with username, password, confirm password
- Auth detection on mount (redirects if already authenticated)
- Client-side validation (empty username, short password, mismatch)
- Server error handling (409 conflict, network errors)
- Welcoming UI with gradient background, dark mode support
- 9 new tests covering all states and error paths
- Updated App.test.tsx to handle async SetupPage rendering
- Added @testing-library/user-event dependency
