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/style-provider/index.native.js

@@ -0,0 +1,3 @@
+export default function StyleProvider( { children } ) {
+	return children;
+}

node_modules/@wordpress/components/src/style-provider/index.tsx

@@ -0,0 +1,48 @@
+/**
+ * External dependencies
+ */
+import { CacheProvider } from '@emotion/react';
+import createCache from '@emotion/cache';
+import * as uuid from 'uuid';
+
+/**
+ * Internal dependencies
+ */
+import type { StyleProviderProps } from './types';
+
+const uuidCache = new Set();
+// Use a weak map so that when the container is detached it's automatically
+// dereferenced to avoid memory leak.
+const containerCacheMap = new WeakMap();
+
+const memoizedCreateCacheWithContainer = ( container: HTMLElement ) => {
+	if ( containerCacheMap.has( container ) ) {
+		return containerCacheMap.get( container );
+	}
+
+	// Emotion only accepts alphabetical and hyphenated keys so we just
+	// strip the numbers from the UUID. It _should_ be fine.
+	let key = uuid.v4().replace( /[0-9]/g, '' );
+	while ( uuidCache.has( key ) ) {
+		key = uuid.v4().replace( /[0-9]/g, '' );
+	}
+	uuidCache.add( key );
+
+	const cache = createCache( { container, key } );
+	containerCacheMap.set( container, cache );
+	return cache;
+};
+
+export function StyleProvider( props: StyleProviderProps ) {
+	const { children, document } = props;
+
+	if ( ! document ) {
+		return null;
+	}
+
+	const cache = memoizedCreateCacheWithContainer( document.head );
+
+	return <CacheProvider value={ cache }>{ children }</CacheProvider>;
+}
+
+export default StyleProvider;

node_modules/@wordpress/components/src/style-provider/types.ts

@@ -0,0 +1,15 @@
+/**
+ * External dependencies
+ */
+import type { ReactNode } from 'react';
+
+export type StyleProviderProps = {
+	/**
+	 * The children elements.
+	 */
+	children: ReactNode;
+	/**
+	 * Current document.
+	 */
+	document: Document;
+};