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/stable/dom-collections/for-each.js

@@ -0,0 +1,6 @@
+'use strict';
+require('../../modules/web.dom-collections.for-each');
+
+var parent = require('../../internals/array-for-each');
+
+module.exports = parent;

node_modules/core-js/stable/dom-collections/index.js

@@ -0,0 +1,14 @@
+'use strict';
+require('../../modules/es.object.to-string');
+require('../../modules/web.dom-collections.for-each');
+require('../../modules/web.dom-collections.iterator');
+var ArrayIterators = require('../../modules/es.array.iterator');
+var forEach = require('../../internals/array-for-each');
+
+module.exports = {
+  keys: ArrayIterators.keys,
+  values: ArrayIterators.values,
+  entries: ArrayIterators.entries,
+  iterator: ArrayIterators.values,
+  forEach: forEach
+};

node_modules/core-js/stable/dom-collections/iterator.js

@@ -0,0 +1,6 @@
+'use strict';
+require('../../modules/es.object.to-string');
+require('../../modules/web.dom-collections.iterator');
+var entryUnbind = require('../../internals/entry-unbind');
+
+module.exports = entryUnbind('Array', 'values');