I want a small demonstration app that runs natively on both iOS and Android. The only feature it needs right now is a basic login and registration flow that talks to a live backend server (any lightweight REST or Firebase-style service is fine as long as the calls are clearly shown). The focus is on clarity rather than polish: clean, well-commented code, simple screens, and a working round-trip of user sign-up, email/password authentication, and sign-in. If you prefer React Native, Flutter, Kotlin Multiplatform, or another modern cross-platform toolkit, feel free to pick the one you are fastest with—just note it in your proposal so I can run and build the project locally. Deliverables • Source code for both platforms in a shared repo • Brief README explaining environment setup, backend endpoints, and how to run on iOS & Android simulators/devices Two interface in billing software • Built test binaries (APK and TestFlight-ready IPA or equivalent) showing the login/registration flow hooked to the backend, I will test by creating an account, signing in, and confirming the API calls succeed, so please include any sample credentials or seed data needed.