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.flat-map.js

@@ -0,0 +1,21 @@
+'use strict';
+var $ = require('../internals/export');
+var flattenIntoArray = require('../internals/flatten-into-array');
+var aCallable = require('../internals/a-callable');
+var toObject = require('../internals/to-object');
+var lengthOfArrayLike = require('../internals/length-of-array-like');
+var arraySpeciesCreate = require('../internals/array-species-create');
+
+// `Array.prototype.flatMap` method
+// https://tc39.es/ecma262/#sec-array.prototype.flatmap
+$({ target: 'Array', proto: true }, {
+  flatMap: function flatMap(callbackfn /* , thisArg */) {
+    var O = toObject(this);
+    var sourceLen = lengthOfArrayLike(O);
+    var A;
+    aCallable(callbackfn);
+    A = arraySpeciesCreate(O, 0);
+    flattenIntoArray(A, O, O, sourceLen, 0, 1, callbackfn, arguments.length > 1 ? arguments[1] : undefined);
+    return A;
+  }
+});