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/eslint-plugin-react/lib/util/report.js

@@ -0,0 +1,12 @@
+'use strict';
+
+const getMessageData = require('./message');
+
+module.exports = function report(context, message, messageId, data) {
+  context.report(
+    Object.assign(
+      getMessageData(messageId, message),
+      data
+    )
+  );
+};