Stripe Integration & Backend Overhaul

Termp Stripe Billing Integration and backend change to support it Add subscription billing so organizations are gated by pricing tier (Free, Solo, Team, LSP). One subscription per org. Current JWT auth is compatible — no auth changes needed... (Budget: $250 - $750 USD, Jobs: JavaScript, Node.js, Payment Processing, Project Management, SaaS, Software Architecture, Software Development, Stripe, Web Development)