m000gg/unit-billing ? reverse-engineered prompt

Build me a simple open source billing system for a service business.

I want an admin area where I can manage customers, services, subscriptions, invoices, payments, and basic automation for recurring billing and service status changes. I also want a customer portal where people can log in, see their account, view invoices, pay bills, and update their details without needing to contact support.

Make it feel clean and easy to use, with a modern dashboard for staff and a straightforward self service experience for customers. Include basic roles so admin and customer views stay separate. If anything is unclear, make sensible choices and keep it practical. Use current best practices and look up any docs online if you need to.