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/build-module/input-control/backdrop.js

@@ -0,0 +1,23 @@
+import { createElement } from "react";
+/**
+ * WordPress dependencies
+ */
+import { memo } from '@wordpress/element';
+/**
+ * Internal dependencies
+ */
+import { BackdropUI } from './styles/input-control-styles';
+function Backdrop({
+  disabled = false,
+  isFocused = false
+}) {
+  return createElement(BackdropUI, {
+    "aria-hidden": "true",
+    className: "components-input-control__backdrop",
+    disabled: disabled,
+    isFocused: isFocused
+  });
+}
+const MemoizedBackdrop = memo(Backdrop);
+export default MemoizedBackdrop;
+//# sourceMappingURL=backdrop.js.map