quantDIY/QuantX — reverse-engineered prompt

Build me a cross platform desktop app called QuantX that works as a trading assistant for TopstepX. I want a clean native feeling desktop window where I can connect my account, manage basic account info, test connectivity, and get set up for live trading and custom strategy work later. The app should keep the desktop layer focused on the interface, with the real logic handled in a backend service, and it should support real time updates for market data and events. Please include a simple onboarding flow that can help create or update the local env settings, and make the whole project easy to run locally with the services starting together for development.

Keep it modular and easy to extend, since this is meant to be a foundation for future trading features, not just a one off demo. Add reasonable tests for both the app side and the backend side, and make sure it works on Windows, Mac, and Ubuntu. If you need details, look up the current TopstepX docs online.