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/randombytes/README.md

@@ -0,0 +1,14 @@
+randombytes
+===
+
+[![Version](http://img.shields.io/npm/v/randombytes.svg)](https://www.npmjs.org/package/randombytes) [![Build Status](https://travis-ci.org/crypto-browserify/randombytes.svg?branch=master)](https://travis-ci.org/crypto-browserify/randombytes)
+
+randombytes from node that works in the browser.  In node you just get crypto.randomBytes, but in the browser it uses .crypto/msCrypto.getRandomValues
+
+```js
+var randomBytes = require('randombytes');
+randomBytes(16);//get 16 random bytes
+randomBytes(16, function (err, resp) {
+  // resp is 16 random bytes
+});
+```