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/2025/PromiseResolve.js

@@ -0,0 +1,18 @@
+'use strict';
+
+var GetIntrinsic = require('get-intrinsic');
+var callBind = require('call-bind');
+var $SyntaxError = require('es-errors/syntax');
+
+var $resolve = GetIntrinsic('%Promise.resolve%', true);
+var $PromiseResolve = $resolve && callBind($resolve);
+
+// https://262.ecma-international.org/9.0/#sec-promise-resolve
+
+module.exports = function PromiseResolve(C, x) {
+	if (!$PromiseResolve) {
+		throw new $SyntaxError('This environment does not support Promises.');
+	}
+	return $PromiseResolve(C, x);
+};
+