flutterando/modular ? reverse-engineered prompt

Build me a Flutter package that helps organize apps by feature with modular routing and dependency injection.

I want a clean setup where each feature can own its routes and services, and the app can be split into small modules instead of one big mess. It should support nested routes, dynamic route params, query strings, route guards, and a persistent shell for shared layout when needed. Also make page scoped state easy, so anything tied to a page gets cleaned up automatically when the route goes away.

Please include a simple example app and a few realistic sample modules like auth, home, and product so I can see how to use it. Keep the public API simple and friendly, with clear docs and tests where it matters. If you need to check the latest Flutter and Dart docs online for best practices, go ahead.