I need a complete mobile application that lets me publish and sell my own service-based inventory in the HVAC spare-parts market. At launch I will be the only seller, so I first need a clean way to upload, edit, and track every item I list. As adoption grows, the architecture must allow me to onboard additional sellers with their own catalogs without rebuilding anything. Buyer access will be invitation-only. That means secure, code-based sign-up flows and an admin console where I can issue, revoke, or monitor invitations at any time. I’m still deciding whether in-app appointment scheduling is necessary, so please structure the back-end in a way that lets us plug that module in later without major refactoring. Deliverables • iOS and Android apps (or a single cross-platform build) connected to a scalable back-end • Admin panel for inventory, invitation management, and multi-seller control • Database seeded with my full HVAC parts catalog, ready for immediate launch Code needs to be clean, documented, and deployed to stores or a test environment I can access.