- src/lib/auth.ts: signIn/signOut/getStoredSession via Supabase Auth REST API
- src/components/LoginPage.tsx: login form with domain validation UI
- src/components/TopBar.tsx: show logged-in user email + sign out button
- src/App.tsx: gate entire app behind auth — shows LoginPage if no session
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>