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/object-inspect/example/inspect.js

@@ -0,0 +1,10 @@
+'use strict';
+
+/* eslint-env browser */
+var inspect = require('../');
+
+var d = document.createElement('div');
+d.setAttribute('id', 'beep');
+d.innerHTML = '<b>wooo</b><i>iiiii</i>';
+
+console.log(inspect([d, { a: 3, b: 4, c: [5, 6, [7, [8, [9]]]] }]));