Add authentication and authorization infrastructure:
- SQLite database (db.rs) with users, sessions, and app permissions tables
- Password hashing with argon2
- Session-based auth with random 256-bit tokens
- Auth middleware (session validation) and admin middleware
- Login/logout/me endpoints
- Admin CRUD endpoints for user and permission management
- Auto-seed default admin user on first run
- 23 unit tests covering all DB operations
Existing API endpoints are not yet gated behind auth.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
restitux