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/es-abstract/2015/RegExpCreate.js

@@ -0,0 +1,21 @@
+'use strict';
+
+var GetIntrinsic = require('get-intrinsic');
+
+var $RegExp = GetIntrinsic('%RegExp%');
+
+// var RegExpAlloc = require('./RegExpAlloc');
+// var RegExpInitialize = require('./RegExpInitialize');
+var ToString = require('./ToString');
+
+// https://262.ecma-international.org/6.0/#sec-regexpcreate
+
+module.exports = function RegExpCreate(P, F) {
+	// var obj = RegExpAlloc($RegExp);
+	// return RegExpInitialize(obj, P, F);
+
+	// covers spec mechanics; bypass regex brand checking
+	var pattern = typeof P === 'undefined' ? '' : ToString(P);
+	var flags = typeof F === 'undefined' ? '' : ToString(F);
+	return new $RegExp(pattern, flags);
+};