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/rechoir/README.md

@@ -0,0 +1,73 @@
+<p align="center">
+  <a href="http://gulpjs.com">
+    <img height="257" width="114" src="https://raw.githubusercontent.com/gulpjs/artwork/master/gulp-2x.png">
+  </a>
+</p>
+
+# rechoir
+
+[![NPM version][npm-image]][npm-url] [![Downloads][downloads-image]][npm-url] [![Build Status][ci-image]][ci-url] [![Coveralls Status][coveralls-image]][coveralls-url]
+
+Prepare a node environment to require files with different extensions.
+
+## What is it?
+
+This module, in conjunction with [interpret]-like objects, can register any filetype the npm ecosystem has a module loader for. This library is a dependency of [liftoff].
+
+**Note:** While `rechoir` will automatically load and register transpilers like `coffee-script`, you must provide a local installation. The transpilers are **not** bundled with this module.
+
+## Usage
+
+```js
+const config = require('interpret').extensions;
+const rechoir = require('rechoir');
+rechoir.prepare(config, './test/fixtures/test.coffee');
+rechoir.prepare(config, './test/fixtures/test.csv');
+rechoir.prepare(config, './test/fixtures/test.toml');
+
+console.log(require('./test/fixtures/test.coffee'));
+console.log(require('./test/fixtures/test.csv'));
+console.log(require('./test/fixtures/test.toml'));
+```
+
+## API
+
+### `prepare(config, filepath, [cwd], [noThrow])`
+
+Look for a module loader associated with the provided file and attempt require it. If necessary, run any setup required to inject it into [require.extensions].
+
+`config` An [interpret]-like configuration object.
+
+`filepath` A file whose type you'd like to register a module loader for.
+
+`cwd` An optional path to start searching for the module required to load the requested file. Defaults to the directory of `filepath`.
+
+`noThrow` An optional boolean indicating if the method should avoid throwing.
+
+If calling this method is successful (e.g. it doesn't throw), you can now require files of the type you requested natively.
+
+An error with a `failures` property will be thrown if the module loader(s) configured for a given extension cannot be registered.
+
+If a loader is already registered, this will simply return `true`.
+
+## License
+
+MIT
+
+<!-- prettier-ignore-start -->
+[downloads-image]: https://img.shields.io/npm/dm/rechoir.svg?style=flat-square
+[npm-url]: https://www.npmjs.com/package/rechoir
+[npm-image]: https://img.shields.io/npm/v/rechoir.svg?style=flat-square
+
+[ci-url]: https://github.com/gulpjs/rechoir/actions?query=workflow:dev
+[ci-image]: https://img.shields.io/github/workflow/status/gulpjs/rechoir/dev?style=flat-square
+
+[coveralls-url]: https://coveralls.io/r/gulpjs/rechoir
+[coveralls-image]: https://img.shields.io/coveralls/gulpjs/rechoir/master.svg
+<!-- prettier-ignore-end -->
+
+<!-- prettier-ignore-start -->
+[interpret]: https://github.com/gulpjs/interpret
+[require.extensions]: https://nodejs.org/api/modules.html#modules_require_extensions
+[liftoff]: https://github.com/js-cli/js-liftoff
+<!-- prettier-ignore-end -->