AI LLM Subscription E-Commerce Site

I’m building a full-stack web platform that sells access to an in-house large-language-model (LLM). The site’s core is e-commerce, but instead of one-off product sales I need subscription services with clear, tiered plans (think “Starter”, “Pro”, “Enterprise”). Each tier will unlock a different usage quota to the model, so the paywall must integrate tightly with the API gateway that fronts the LLM.

Scope of work
• Design a responsive customer-facing site where visitors can learn about the model, compare tiers, and sign up.
• Implement secure user authentication, payment processing, and a dashboard where subscribers can view remaining tokens, upgrade/downgrade, or cancel.
• Build the back-end that meters requests to the LLM by tier and logs usage for transparent billing.
• Provide an admin console for me to create new tiers, adjust pricing, and view analytics.
• Deploy the stack (preferred toolset: React or Next.js on the front end, Node/Express or Python/FastAPI on the back end, Stripe for payments, and a relational DB) to a cloud host of your choice.

Acceptance criteria
1. A new user can register, choose a tier, pay, and immediately receive an API key scoped to that tier.
2. Usage throttling kicks in when limits are reached and resets automatically on renewal.
3. Tier changes prorate correctly.
4. Admin actions update live without downtime.
5. Codebase is delivered in a Git repo with a README covering local setup, env vars, and deployment commands.

If you have previous experience building subscription SaaS or AI tool marketplaces, that will help us move fast. Let me know your preferred stack, estimated timeline, and any clarifying questions.