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/priority-queue/build-module/request-idle-callback.js

@@ -0,0 +1,22 @@
+/**
+ * External dependencies
+ */
+import 'requestidlecallback';
+
+/**
+ * @typedef {( timeOrDeadline: IdleDeadline | number ) => void} Callback
+ */
+
+/**
+ * @return {(callback: Callback) => void} RequestIdleCallback
+ */
+export function createRequestIdleCallback() {
+  if (typeof window === 'undefined') {
+    return callback => {
+      setTimeout(() => callback(Date.now()), 0);
+    };
+  }
+  return window.requestIdleCallback;
+}
+export default createRequestIdleCallback();
+//# sourceMappingURL=request-idle-callback.js.map