medusajs/medusa ? reverse-engineered prompt

I want to build a flexible, open-source e-commerce platform. Think of it as a headless alternative to Shopify; it should be a backend-first system using Node.js and TypeScript that provides the core building blocks for digital commerce.

The main goal is to create a customizable foundation that could be used for many kinds of projects, like a B2B store, a marketplace, or a custom direct-to-consumer site. It should include all the essential features: product management with variants, a cart system, customer accounts, and an order processing flow. Make the architecture modular so it's easy to add new features or integrations later. For now, you don't need to build a full frontend, but make sure the API is clean and ready to be used by any storefront.