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/@hapi/hoek/lib/reachTemplate.js

@@ -0,0 +1,16 @@
+'use strict';
+
+const Reach = require('./reach');
+
+
+const internals = {};
+
+
+module.exports = function (obj, template, options) {
+
+    return template.replace(/{([^{}]+)}/g, ($0, chain) => {
+
+        const value = Reach(obj, chain, options);
+        return (value === undefined || value === null ? '' : value);
+    });
+};