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/2016/IterableToArrayLike.js

@@ -0,0 +1,34 @@
+'use strict';
+
+var getIteratorMethod = require('../helpers/getIteratorMethod');
+var AdvanceStringIndex = require('./AdvanceStringIndex');
+var GetIterator = require('./GetIterator');
+var GetMethod = require('./GetMethod');
+var IteratorStep = require('./IteratorStep');
+var IteratorValue = require('./IteratorValue');
+var ToObject = require('./ToObject');
+var ES = {
+	AdvanceStringIndex: AdvanceStringIndex,
+	GetMethod: GetMethod
+};
+
+// https://262.ecma-international.org/7.0/#sec-iterabletoarraylike
+
+module.exports = function IterableToArrayLike(items) {
+	var usingIterator = getIteratorMethod(ES, items);
+	if (typeof usingIterator !== 'undefined') {
+		var iterator = GetIterator(items, usingIterator);
+		var values = [];
+		var next = true;
+		while (next) {
+			next = IteratorStep(iterator);
+			if (next) {
+				var nextValue = IteratorValue(next);
+				values[values.length] = nextValue;
+			}
+		}
+		return values;
+	}
+
+	return ToObject(items);
+};