Flutter Pedometer App Enhancement

I'm seeking an experienced Flutter developer to upgrade my existing basic pedometer app on Android. The app currently tracks daily steps, and I’d like to enhance it by adding new features to improve usability and user engagement.

Required Features:
- Weekly and monthly step statistics
- Dark mode support
- Notifications to remind users to stay active
- A simple graphic or chart to show activity trends
- UI improvements with a clean, lightweight look following Material Design
- (Optional) Basic login system or local user data management

The ideal candidate should:
- Have solid experience with Flutter
- Be able to implement these new features cleanly within the existing codebase
- Have a strong understanding of Material Design principles