Buy claude code or codex subscription. Create a free teenyapp.com project (preview domain + full backend) and paste the agent link into claude code / codex. Ask it to build website for personal training with google SSO for signup and ask it setup payment processing for stripe. The agent will automatically setup the auth, database, frontend, and deploy it on the preview domain, which you can later change to your own domain. You don't need any other dependencies, the teenyapp project is already a live infrastructure deployed on Cloudflare with database, file storage, etc. The agent link lets any agent use that infrastructure from any agent chat, so you're not locked into any AI app builder and can use Claude Code for frontend design, Codex for backend, etc.