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/axios/lib/platform/common/utils.js

@@ -0,0 +1,52 @@
+const hasBrowserEnv = typeof window !== 'undefined' && typeof document !== 'undefined';
+
+const _navigator = (typeof navigator === 'object' && navigator) || undefined;
+
+/**
+ * Determine if we're running in a standard browser environment
+ *
+ * This allows axios to run in a web worker, and react-native.
+ * Both environments support XMLHttpRequest, but not fully standard globals.
+ *
+ * web workers:
+ *  typeof window -> undefined
+ *  typeof document -> undefined
+ *
+ * react-native:
+ *  navigator.product -> 'ReactNative'
+ * nativescript
+ *  navigator.product -> 'NativeScript' or 'NS'
+ *
+ * @returns {boolean}
+ */
+const hasStandardBrowserEnv =
+  hasBrowserEnv &&
+  (!_navigator || ['ReactNative', 'NativeScript', 'NS'].indexOf(_navigator.product) < 0);
+
+/**
+ * Determine if we're running in a standard browser webWorker environment
+ *
+ * Although the `isStandardBrowserEnv` method indicates that
+ * `allows axios to run in a web worker`, the WebWorker will still be
+ * filtered out due to its judgment standard
+ * `typeof window !== 'undefined' && typeof document !== 'undefined'`.
+ * This leads to a problem when axios post `FormData` in webWorker
+ */
+const hasStandardBrowserWebWorkerEnv = (() => {
+  return (
+    typeof WorkerGlobalScope !== 'undefined' &&
+    // eslint-disable-next-line no-undef
+    self instanceof WorkerGlobalScope &&
+    typeof self.importScripts === 'function'
+  );
+})();
+
+const origin = (hasBrowserEnv && window.location.href) || 'http://localhost';
+
+export {
+  hasBrowserEnv,
+  hasStandardBrowserWebWorkerEnv,
+  hasStandardBrowserEnv,
+  _navigator as navigator,
+  origin,
+};