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/core-js/modules/es.reflect.get.js

@@ -0,0 +1,27 @@
+'use strict';
+var $ = require('../internals/export');
+var call = require('../internals/function-call');
+var isObject = require('../internals/is-object');
+var anObject = require('../internals/an-object');
+var isDataDescriptor = require('../internals/is-data-descriptor');
+var getOwnPropertyDescriptorModule = require('../internals/object-get-own-property-descriptor');
+var getPrototypeOf = require('../internals/object-get-prototype-of');
+var toPropertyKey = require('../internals/to-property-key');
+
+// `Reflect.get` method
+// https://tc39.es/ecma262/#sec-reflect.get
+var $get = function (target, propertyKey, receiver) {
+  if (anObject(target) === receiver) return target[propertyKey];
+  var descriptor = getOwnPropertyDescriptorModule.f(target, propertyKey);
+  if (descriptor) return isDataDescriptor(descriptor)
+    ? descriptor.value
+    : descriptor.get === undefined ? undefined : call(descriptor.get, receiver);
+  var prototype = getPrototypeOf(target);
+  if (isObject(prototype)) return $get(prototype, propertyKey, receiver);
+};
+
+$({ target: 'Reflect', stat: true }, {
+  get: function get(target, propertyKey /* , receiver */) {
+    return $get(anObject(target), toPropertyKey(propertyKey), arguments.length < 3 ? target : arguments[2]);
+  }
+});