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/2023/Invoke.js

@@ -0,0 +1,22 @@
+'use strict';
+
+var $TypeError = require('es-errors/type');
+
+var Call = require('./Call');
+var IsArray = require('./IsArray');
+var GetV = require('./GetV');
+var isPropertyKey = require('../helpers/isPropertyKey');
+
+// https://262.ecma-international.org/6.0/#sec-invoke
+
+module.exports = function Invoke(O, P) {
+	if (!isPropertyKey(P)) {
+		throw new $TypeError('Assertion failed: P must be a Property Key');
+	}
+	var argumentsList = arguments.length > 2 ? arguments[2] : [];
+	if (!IsArray(argumentsList)) {
+		throw new $TypeError('Assertion failed: optional `argumentsList`, if provided, must be a List');
+	}
+	var func = GetV(O, P);
+	return Call(func, O, argumentsList);
+};