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/escapeJson.js

@@ -0,0 +1,28 @@
+'use strict';
+
+const internals = {};
+
+
+module.exports = function (input) {
+
+    if (!input) {
+        return '';
+    }
+
+    return input.replace(/[<>&\u2028\u2029]/g, internals.escape);
+};
+
+
+internals.escape = function (char) {
+
+    return internals.replacements.get(char);
+};
+
+
+internals.replacements = new Map([
+    ['<', '\\u003c'],
+    ['>', '\\u003e'],
+    ['&', '\\u0026'],
+    ['\u2028', '\\u2028'],
+    ['\u2029', '\\u2029']
+]);