feat: add user role types and auth middleware
- lib/auth/roles.ts: UserRole union, ALL_ROLES, ROLE_HOME, getRoleHome, isValidRole (pure, no Supabase imports)
- __tests__/lib/auth/roles.test.ts: 8 TDD tests (written before implementation)
- middleware.ts: createServerClient with request.cookies pattern, unauthenticated redirect to /login, role-based redirect on / and /login
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AWxyMibCuGGtSQSqfajDQ7