I’ve already built a full-featured billing and inventory web app for ASK INDUSTRIAL WORKS with vanilla HTML, CSS, JavaScript, and localStorage. Now I need a lean authentication layer so different users see only what they should. Scope • Add a simple login screen that stores credentials locally (no external database—keep using localStorage). • Create three roles: Admin, Manager, Staff. • Apply access rules: – Admin: everything. – Manager: approve payments, generate reports, manage products and inventory. – Staff: day-to-day billing and stock entries only. • Hide or disable UI elements based on the active role. • Maintain the responsive, printable layout and existing reporting logic. • Deliver clean, well-commented code plus a short README so I can extend it later. Tech constraints Pure JavaScript front-end, Python only if you need a lightweight helper script—but no new frameworks or back-end services. If you’ve implemented lightweight role-based security in front-end apps before, I’d love to see a quick example when you bid.