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/icons/build-module/library/html.js

@@ -0,0 +1,13 @@
+import { createElement } from "react";
+/**
+ * WordPress dependencies
+ */
+import { SVG, Path } from '@wordpress/primitives';
+const html = createElement(SVG, {
+  viewBox: "0 0 24 24",
+  xmlns: "http://www.w3.org/2000/svg"
+}, createElement(Path, {
+  d: "M4.8 11.4H2.1V9H1v6h1.1v-2.6h2.7V15h1.1V9H4.8v2.4zm1.9-1.3h1.7V15h1.1v-4.9h1.7V9H6.7v1.1zM16.2 9l-1.5 2.7L13.3 9h-.9l-.8 6h1.1l.5-4 1.5 2.8 1.5-2.8.5 4h1.1L17 9h-.8zm3.8 5V9h-1.1v6h3.6v-1H20z"
+}));
+export default html;
+//# sourceMappingURL=html.js.map