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.array.map.js

@@ -0,0 +1,15 @@
+'use strict';
+var $ = require('../internals/export');
+var $map = require('../internals/array-iteration').map;
+var arrayMethodHasSpeciesSupport = require('../internals/array-method-has-species-support');
+
+var HAS_SPECIES_SUPPORT = arrayMethodHasSpeciesSupport('map');
+
+// `Array.prototype.map` method
+// https://tc39.es/ecma262/#sec-array.prototype.map
+// with adding support of @@species
+$({ target: 'Array', proto: true, forced: !HAS_SPECIES_SUPPORT }, {
+  map: function map(callbackfn /* , thisArg */) {
+    return $map(this, callbackfn, arguments.length > 1 ? arguments[1] : undefined);
+  }
+});