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/insert-after.js

@@ -0,0 +1,13 @@
+import { createElement } from "react";
+/**
+ * WordPress dependencies
+ */
+import { SVG, Path } from '@wordpress/primitives';
+const insertAfter = createElement(SVG, {
+  xmlns: "http://www.w3.org/2000/svg",
+  viewBox: "-2 -2 24 24"
+}, createElement(Path, {
+  d: "M9 12h2v-2h2V8h-2V6H9v2H7v2h2v2zm1 4c3.9 0 7-3.1 7-7s-3.1-7-7-7-7 3.1-7 7 3.1 7 7 7zm0-12c2.8 0 5 2.2 5 5s-2.2 5-5 5-5-2.2-5-5 2.2-5 5-5zM3 19h14v-2H3v2z"
+}));
+export default insertAfter;
+//# sourceMappingURL=insert-after.js.map