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/error-stack-parser/README.md

@@ -0,0 +1,44 @@
+error-stack-parser.js - Extract meaning from JS Errors
+===============
+[![Build Status](https://img.shields.io/github/workflow/status/stacktracejs/error-stack-parser/Continuous%20Integration/master?logo=github&style=flat-square)](https://github.com/stacktracejs/error-stack-parser/actions?query=workflow%3AContinuous+Integration+branch%3Amaster)
+[![Coverage Status](https://img.shields.io/coveralls/stacktracejs/error-stack-parser.svg?style=flat-square)](https://coveralls.io/r/stacktracejs/error-stack-parser?branch=master)
+[![GitHub license](https://img.shields.io/github/license/stacktracejs/error-stack-parser.svg?style=flat-square)](https://opensource.org/licenses/MIT)
+[![size with dependencies](https://img.shields.io/badge/size-4.8k-green.svg?style=flat-square)](https://github.com/stacktracejs/error-stack-parser/releases)
+[![gzip size](https://img.shields.io/badge/gzipped-1.8k-green.svg?style=flat-square)](https://github.com/stacktracejs/error-stack-parser/releases)
+[![module format](https://img.shields.io/badge/module%20format-umd-lightgrey.svg?style=flat-square&colorB=ff69b4)](https://github.com/stacktracejs/error-stack-parser/releases)
+[![code of conduct](https://img.shields.io/badge/code%20of-conduct-lightgrey.svg?style=flat-square&colorB=ff69b4)](http://todogroup.org/opencodeofconduct/#stacktrace.js/me@eriwen.com)
+[![jsDelivr Hits](https://data.jsdelivr.com/v1/package/npm/error-stack-parser/badge)](https://www.jsdelivr.com/package/npm/error-stack-parser)
+
+Simple, cross-browser [Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error) parser.
+This library parses and extracts function names, URLs, line numbers, and column numbers from the given Error's `stack` as
+an Array of [StackFrame](http://git.io/stackframe)s. 
+
+Once you have parsed out StackFrames, you can do much more interesting things. See [stacktrace-gps](http://git.io/stacktrace-gps).
+
+Note that in IE9 and earlier, `Error` objects don't have enough information to extract much of anything. In IE 10, `Error`s
+are given a `stack` once they're `throw`n.
+
+## Browser Support
+[![Sauce Test Status](https://saucelabs.com/browser-matrix/stacktracejs.svg)](https://saucelabs.com/u/stacktracejs)
+
+## Usage
+```js
+ErrorStackParser.parse(new Error('BOOM'));
+
+=> [
+        StackFrame({functionName: 'foo', args: [], fileName: 'path/to/file.js', lineNumber: 35, columnNumber: 79, isNative: false, isEval: false}),
+        StackFrame({functionName: 'Bar', fileName: 'https://cdn.somewherefast.com/utils.min.js', lineNumber: 1, columnNumber: 832, isNative: false, isEval: false, isConstructor: true}),
+        StackFrame(... and so on ...)
+   ]
+```
+
+## Installation
+```bash
+npm install error-stack-parser
+bower install error-stack-parser
+https://raw.githubusercontent.com/stacktracejs/error-stack-parser/master/dist/error-stack-parser.min.js
+```
+
+## Contributing
+Want to be listed as a *Contributor*? Start with the [Contributing Guide](.github/CONTRIBUTING.md)!
+