Flutter Cross-Platform App Development

I’m building a single code-base mobile app with Flutter and Dart that must run smoothly on both Android and iOS. Core screens include onboarding, login, sign-up, and a protected area once users are authenticated.

Firebase will handle the back-end side of things, so expect real-time database or Firestore, authentication, and possibly analytics to come into play. I already have several REST endpoints documented in Swagger; please wire those up for data fetch and submission. If you see gaps or optimisation opportunities, I’m happy to adjust the API layer together.

The finished deliverable should be a clean, well-structured Flutter project that compiles for Android and iOS, includes all authentication flows, integrates each required Firebase service, and hits my REST endpoints with proper error handling. Provide the source code in a private Git repo and a brief README explaining setup, build steps, and any environment variables.