purpleBox method
Wraps the widget in a ColoredBox with system purple color.
Uses CupertinoColors.systemPurple which adapts to light/dark mode. This is the standard purple color used throughout iOS interfaces, often used for creative or premium features.
Returns a ColoredBox containing the current widget with purple background.
Example:
Icon(CupertinoIcons.star).purpleBox()
Implementation
ColoredBox purpleBox() => coloredBox(CupertinoColors.systemPurple);