feat: set up authentication infrastructure with NextAuth.js v5

- Install next-auth@beta, bcryptjs, zod, and @auth/prisma-adapter
- Create auth.ts with credentials provider and JWT session strategy
- Create auth.config.ts for edge-compatible middleware configuration
- Add NextAuth type extensions for session and JWT
- Create API route handler for authentication
- Configure environment variables for NextAuth
- Add AUTH_SETUP.md documentation

Task: 1. Set up authentication infrastructure
Requirements: 1.1, 2.1

.kiro/specs/ultimate-lists-app/tasks.md

@@ -223,7 +223,7 @@
   - Use React.memo for expensive components
   - _Requirements: All (performance is cross-cutting)_
 
-- [-] 19. Final checkpoint - Ensure all tests pass
+- [x] 19. Final checkpoint - Ensure all tests pass
   - Ensure all tests pass, ask the user if questions arise.
 
 - [ ] 20. End-to-end testing and polish