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

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+# 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

node_modules/@wordpress/components/src/tree-select/index.tsx

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+/**
+ * WordPress dependencies
+ */
+import { useMemo } from '@wordpress/element';
+import { decodeEntities } from '@wordpress/html-entities';
+
+/**
+ * Internal dependencies
+ */
+import { SelectControl } from '../select-control';
+import type { TreeSelectProps, Tree, Truthy } from './types';
+import { useDeprecated36pxDefaultSizeProp } from '../utils/use-deprecated-props';
+
+function getSelectOptions(
+	tree: Tree[],
+	level = 0
+): NonNullable< TreeSelectProps[ 'options' ] > {
+	return tree.flatMap( ( treeNode ) => [
+		{
+			value: treeNode.id,
+			label:
+				'\u00A0'.repeat( level * 3 ) + decodeEntities( treeNode.name ),
+		},
+		...getSelectOptions( treeNode.children || [], level + 1 ),
+	] );
+}
+
+/**
+ * TreeSelect component is used to generate select input fields.
+ *
+ * ```jsx
+ * import { TreeSelect } from '@wordpress/components';
+ * import { useState } from '@wordpress/element';
+ *
+ * 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',
+ * 								},
+ * 							],
+ * 						},
+ * 					],
+ * 				},
+ * 			] }
+ * 		/>
+ * 	);
+ * }
+ * ```
+ */
+
+export function TreeSelect( props: TreeSelectProps ) {
+	const {
+		label,
+		noOptionLabel,
+		onChange,
+		selectedId,
+		tree = [],
+		...restProps
+	} = useDeprecated36pxDefaultSizeProp(
+		props,
+		'wp.components.TreeSelect',
+		'6.4'
+	);
+
+	const options = useMemo( () => {
+		return [
+			noOptionLabel && { value: '', label: noOptionLabel },
+			...getSelectOptions( tree ),
+		].filter( < T, >( option: T ): option is Truthy< T > => !! option );
+	}, [ noOptionLabel, tree ] );
+
+	return (
+		<SelectControl
+			{ ...{ label, options, onChange } }
+			value={ selectedId }
+			{ ...restProps }
+		/>
+	);
+}
+
+export default TreeSelect;

node_modules/@wordpress/components/src/tree-select/stories/index.story.tsx

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+/**
+ * External dependencies
+ */
+import type { Meta, StoryFn } from '@storybook/react';
+import type { ComponentProps } from 'react';
+/**
+ * WordPress dependencies
+ */
+import { useState } from '@wordpress/element';
+
+/**
+ * Internal dependencies
+ */
+import TreeSelect from '../';
+
+const meta: Meta< typeof TreeSelect > = {
+	title: 'Components/TreeSelect',
+	component: TreeSelect,
+	argTypes: {
+		help: { control: { type: 'text' } },
+		label: { control: { type: 'text' } },
+		prefix: { control: { type: 'text' } },
+		suffix: { control: { type: 'text' } },
+		selectedId: { control: { type: null } },
+	},
+	parameters: {
+		controls: {
+			expanded: true,
+		},
+		docs: { canvas: { sourceState: 'shown' } },
+	},
+};
+
+export default meta;
+
+const TreeSelectWithState: StoryFn< typeof TreeSelect > = ( props ) => {
+	const [ selection, setSelection ] =
+		useState< ComponentProps< typeof TreeSelect >[ 'selectedId' ] >();
+
+	return (
+		<TreeSelect
+			{ ...props }
+			onChange={ setSelection }
+			selectedId={ selection }
+		/>
+	);
+};
+
+export const Default = TreeSelectWithState.bind( {} );
+Default.args = {
+	label: 'Label Text',
+	noOptionLabel: 'No parent page',
+	help: 'Help text to explain the select control.',
+	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',
+						},
+					],
+				},
+			],
+		},
+	],
+};

node_modules/@wordpress/components/src/tree-select/types.ts

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+/**
+ * Internal dependencies
+ */
+import type { SelectControlSingleSelectionProps } from '../select-control/types';
+
+export type Truthy< T > = T extends false | '' | 0 | null | undefined
+	? never
+	: T;
+
+export interface Tree {
+	id: string;
+	name: string;
+	children?: Tree[];
+}
+
+// `TreeSelect` inherits props from `SelectControl`, but only
+// in single selection mode (ie. when the `multiple` prop is not defined).
+export interface TreeSelectProps
+	extends Omit< SelectControlSingleSelectionProps, 'value' | 'multiple' > {
+	/**
+	 * If this property is added, an option will be added with this label to represent empty selection.
+	 */
+	noOptionLabel?: string;
+	/**
+	 * An array containing the tree objects with the possible nodes the user can select.
+	 */
+	tree?: Tree[];
+	/**
+	 * The id of the currently selected node.
+	 */
+	selectedId?: SelectControlSingleSelectionProps[ 'value' ];
+}