UI & Widgets (P1)

• State: Use StatelessWidget by default. StatefulWidget only for local state/controllers.
• Composition: Extract UI into small, atomic const widgets.
• Theming: Use Theme.of(context). No hardcoded colors.
• Layout: Use Flex + Gap/SizedBox.
• Specialized:
  • SelectionArea: For multi-widget text selection.
  • InteractiveViewer: For zoom/pan.
  • ListWheelScrollView: For pickers.
  • IntrinsicWidth/Height: Avoid unless strictly required.
• Large Lists: Always use ListView.builder.

class AppButton extends StatelessWidget {
  final String label;
  final VoidCallback onPressed;
  const AppButton({super.key, required this.label, required this.onPressed});