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/loader-utils/lib/getCurrentRequest.js

@@ -0,0 +1,16 @@
+'use strict';
+
+function getCurrentRequest(loaderContext) {
+  if (loaderContext.currentRequest) {
+    return loaderContext.currentRequest;
+  }
+
+  const request = loaderContext.loaders
+    .slice(loaderContext.loaderIndex)
+    .map((obj) => obj.request)
+    .concat([loaderContext.resource]);
+
+  return request.join('!');
+}
+
+module.exports = getCurrentRequest;