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/focusable-iframe/index.js

@@ -0,0 +1,29 @@
+import { createElement } from "react";
+/**
+ * WordPress dependencies
+ */
+import { useMergeRefs, useFocusableIframe } from '@wordpress/compose';
+import deprecated from '@wordpress/deprecated';
+/**
+ * Internal dependencies
+ */
+
+export default function FocusableIframe({
+  iframeRef,
+  ...props
+}) {
+  const ref = useMergeRefs([iframeRef, useFocusableIframe()]);
+  deprecated('wp.components.FocusableIframe', {
+    since: '5.9',
+    alternative: 'wp.compose.useFocusableIframe'
+  });
+  // Disable reason: The rendered iframe is a pass-through component,
+  // assigning props inherited from the rendering parent. It's the
+  // responsibility of the parent to assign a title.
+  // eslint-disable-next-line jsx-a11y/iframe-has-title
+  return createElement("iframe", {
+    ref: ref,
+    ...props
+  });
+}
+//# sourceMappingURL=index.js.map