Production-ready Dart and Flutter patterns covering null safety, immutable state, async composition, widget architecture, popular state management frameworks (BLoC, Riverpod, Provider), GoRouter navigation, Dio networking, Freezed code generation, and clean architecture. Use when writing or reviewing Dart and Flutter code — state, widgets, navigation, networking, or architecture. It provides copy-paste-ready Dart and Flutter code patterns organized by concern to guide developers through idiomatic implementation.