fix: prevent asset conflicts between React and Grid.js versions

Add coexistence checks to all enqueue methods to prevent loading
both React and Grid.js assets simultaneously.

Changes:
- ReactAdmin.php: Only enqueue React assets when ?react=1
- Init.php: Skip Grid.js when React active on admin pages
- Form.php, Coupon.php, Access.php: Restore classic assets when ?react=0
- Customer.php, Product.php, License.php: Add coexistence checks

Now the toggle between Classic and React versions works correctly.

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

node_modules/@wordpress/components/src/base-control/hooks.ts

@@ -0,0 +1,45 @@
+/**
+ * WordPress dependencies
+ */
+import { useInstanceId } from '@wordpress/compose';
+
+/**
+ * Internal dependencies
+ */
+import BaseControl from '.';
+import type { BaseControlProps } from './types';
+
+/**
+ * Generate props for the `BaseControl` and the inner control itself.
+ *
+ * Namely, it takes care of generating a unique `id`, properly associating it with the `label` and `help` elements.
+ *
+ * @param props
+ */
+export function useBaseControlProps(
+	props: Omit< BaseControlProps, 'children' >
+) {
+	const { help, id: preferredId, ...restProps } = props;
+
+	const uniqueId = useInstanceId(
+		BaseControl,
+		'wp-components-base-control',
+		preferredId
+	);
+
+	// ARIA descriptions can only contain plain text, so fall back to aria-details if not.
+	const helpPropName =
+		typeof help === 'string' ? 'aria-describedby' : 'aria-details';
+
+	return {
+		baseControlProps: {
+			id: uniqueId,
+			help,
+			...restProps,
+		},
+		controlProps: {
+			id: uniqueId,
+			...( !! help ? { [ helpPropName ]: `${ uniqueId }__help` } : {} ),
+		},
+	};
+}