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/on-headers/HISTORY.md

@@ -0,0 +1,26 @@
+1.1.0 / 2025-07-17
+==================
+  * - Fix [CVE-2025-7339](https://www.cve.org/CVERecord?id=CVE-2025-7339) ([GHSA-76c9-3jph-rj3q](https://github.com/expressjs/multer/security/advisories/GHSA-76c9-3jph-rj3q))
+
+
+1.0.2 / 2019-02-21
+==================
+
+  * Fix `res.writeHead` patch missing return value
+
+1.0.1 / 2015-09-29
+==================
+
+  * perf: enable strict mode
+
+1.0.0 / 2014-08-10
+==================
+
+  * Honor `res.statusCode` change in `listener`
+  * Move to `jshttp` organization
+  * Prevent `arguments`-related de-opt
+
+0.0.0 / 2014-05-13
+==================
+
+  * Initial implementation