Checkbox from @kibrisyazilim/design-system. Use via `window.KibrisDS.Checkbox` (bundle loaded from the root `_ds_bundle.js`).

Single checkbox with an optional label and description.

## Props

```ts
interface CheckboxProps {
  /** Text beside the box. */
  label?: React.ReactNode;
  /** Secondary line under the label. */
  description?: React.ReactNode;
  /** Renders the mixed state. Visual only — `checked` still drives the value. */
  indeterminate?: boolean;
  /** Puts the box in its invalid state. */
  invalid?: boolean;
  className?: string;
  id?: string;
  style?: CSSProperties;
  children?: React.ReactNode;
}
```