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/jest-haste-map/build/lib/isWatchmanInstalled.js

@@ -0,0 +1,37 @@
+'use strict';
+
+Object.defineProperty(exports, '__esModule', {
+  value: true
+});
+exports.default = isWatchmanInstalled;
+function _child_process() {
+  const data = require('child_process');
+  _child_process = function () {
+    return data;
+  };
+  return data;
+}
+function _util() {
+  const data = require('util');
+  _util = function () {
+    return data;
+  };
+  return data;
+}
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+async function isWatchmanInstalled() {
+  try {
+    await (0, _util().promisify)(_child_process().execFile)('watchman', [
+      '--version'
+    ]);
+    return true;
+  } catch {
+    return false;
+  }
+}