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/builtin-modules/index.js

@@ -0,0 +1,11 @@
+'use strict';
+const {builtinModules} = require('module');
+
+const ignoreList = [
+	'sys'
+];
+
+// eslint-disable-next-line node/no-deprecated-api
+module.exports = (builtinModules || (process.binding ? Object.keys(process.binding('natives')) : []) || [])
+	.filter(x => !/^_|^(internal|v8|node-inspect)\/|\//.test(x) && !ignoreList.includes(x))
+	.sort();