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/tree-select/README.md

@@ -0,0 +1,91 @@
+# TreeSelect
+
+TreeSelect component is used to generate select input fields.
+
+## Usage
+
+Render a user interface to select the parent page in a hierarchy of pages:
+
+```jsx
+import { useState } from 'react';
+import { TreeSelect } from '@wordpress/components';
+
+const MyTreeSelect = () => {
+	const [ page, setPage ] = useState( 'p21' );
+
+	return (
+		<TreeSelect
+			label="Parent page"
+			noOptionLabel="No parent page"
+			onChange={ ( newPage ) => setPage( newPage ) }
+			selectedId={ page }
+			tree={ [
+				{
+					name: 'Page 1',
+					id: 'p1',
+					children: [
+						{ name: 'Descend 1 of page 1', id: 'p11' },
+						{ name: 'Descend 2 of page 1', id: 'p12' },
+					],
+				},
+				{
+					name: 'Page 2',
+					id: 'p2',
+					children: [
+						{
+							name: 'Descend 1 of page 2',
+							id: 'p21',
+							children: [
+								{
+									name: 'Descend 1 of Descend 1 of page 2',
+									id: 'p211',
+								},
+							],
+						},
+					],
+				},
+			] }
+		/>
+	);
+}
+```
+
+## Props
+
+The set of props accepted by the component will be specified below.
+Props not included in this set will be applied to the SelectControl component being used.
+
+### label
+
+If this property is added, a label will be generated using label property as the content.
+
+-   Type: `String`
+-   Required: No
+
+### noOptionLabel
+
+If this property is added, an option will be added with this label to represent empty selection.
+
+-   Type: `String`
+-   Required: No
+
+### onChange
+
+A function that receives the id of the new node element that is being selected.
+
+-   Type: `function`
+-   Required: Yes
+
+### selectedId
+
+The id of the currently selected node.
+
+-   Type: `string` | `string[]`
+-   Required: No
+
+### tree
+
+An array containing the tree objects with the possible nodes the user can select.
+
+-   Type: `Object[]`
+-   Required: No