Senior Full-Stack Engineer for Education Platform

Seeking a senior full-stack engineer to build a secure, scalable, production-ready international education platform from an existing design. The platform must include student accounts, course management, an admin dashboard, protected video lessons, and subscription plans ($20/month or $69/year), supporting Arabic, English, and French with RTL. Security and reliability are critical: robust PostgreSQL architecture, Supabase Auth, strict RLS, server-side authorization, secure session handling, input validation, rate limiting, protection against common web attacks, verified payment webhooks, audit logs, encrypted secrets, backups, monitoring, and tested recovery procedures. No fake payments or placeholder security. Please review the existing project before making changes. Provide relevant live projects, your security approach, architecture, timeline, milestone-based costs, source code, deployment documentation, and security testing. Verify payment-provider eligibility for an Algerian business before integration.