ChartController class

ChangeNotifier-based controller for programmatic chart updates.

Manages chart data and annotations, providing methods for real-time updates with automatic listener notification.

Example:

final controller = ChartController();

// Add data points
controller.addPoint('temperature', ChartDataPoint(x: 0, y: 20.0));
controller.addPoint('temperature', ChartDataPoint(x: 1, y: 22.5));

// Add annotations
controller.addAnnotation(
  TextAnnotation(
    position: Offset(100, 50),
    label: 'High temp alert',
  ),
);

// Clean up
controller.dispose();