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/regjsgen/README.md

@@ -0,0 +1,41 @@
+# regjsgen [![Build status][ci-img]][ci] [![Code coverage status][codecov-img]][codecov]
+
+Generate regular expressions from [regjsparser][regjsparser]’s AST.
+
+## Installation
+
+```sh
+npm i regjsgen
+```
+
+## API
+
+### `regjsgen.generate(ast)`
+
+This function accepts an abstract syntax tree representing a regular expression (see [regjsparser][regjsparser]), and returns the generated regular expression string.
+
+```js
+const regjsparser = require('regjsparser');
+const regjsgen = require('regjsgen');
+
+// Generate an AST with `regjsparser`.
+let ast = regjsparser.parse(regex);
+
+// Modify AST
+// …
+
+// Generate `RegExp` string with `regjsgen`.
+let regex = regjsgen.generate(ast);
+```
+
+## Support
+
+Tested on Node.js 16 and 18.<br>
+Compatible with regjsparser v0.10.0’s AST.
+
+
+[ci]: https://github.com/bnjmnt4n/regjsgen/actions
+[ci-img]: https://github.com/bnjmnt4n/regjsgen/workflows/Node.js%20CI/badge.svg
+[codecov]: https://codecov.io/gh/bnjmnt4n/regjsgen
+[codecov-img]: https://codecov.io/gh/bnjmnt4n/regjsgen/branch/main/graph/badge.svg
+[regjsparser]: https://github.com/jviereck/regjsparser