I need a mobile application written in C# that installs and runs natively on both iOS and Android. The single most important feature is rock-solid user authentication—think sign-up, secure login, session handling, and a clean hand-off for token renewal. You are free to choose Xamarin.Forms or the newer .NET MAUI stack so long as the resulting solution compiles and deploys cleanly through Xcode and Android Studio. The goal is a working, developer-friendly baseline app. Screens can be simple placeholders; code quality, security practices, and clear separation of concerns matter far more than polished UI at this stage. Deliverables • Complete C# source in a Git-ready repository • iOS and Android project folders that build without modification • Login / register screens wired to an in-code mock API layer (ready to swap for a real endpoint) • Token storage that survives app restarts, using Keychain / Keystore • README with build instructions and a brief architecture overview I will test by cloning, restoring NuGet packages, and deploying to both simulators. If everything authenticates, persists a session, and logs out cleanly, we’re done.