SubZeroDialogContentArea class

A pre-built content widget for dialogs with placeholder content area.

This widget provides a consistent structure matching the Figma design with a gray content placeholder area that can hold images, forms, etc.

Example usage:

showSubZeroDialog(
  context: context,
  title: 'Upload Image',
  content: SubZeroDialogContentArea(
    height: 120,
    child: Icon(Icons.cloud_upload, size: 48, color: SubZeroColors.textTertiary),
  ),
  body: 'Drag and drop an image or click to browse.',
  actions: SubZeroDialogActions(
    primaryLabel: 'Upload',
    secondaryLabel: 'Cancel',
  ),
);