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/redent/readme.md

@@ -0,0 +1,61 @@
+# redent [![Build Status](https://travis-ci.org/sindresorhus/redent.svg?branch=master)](https://travis-ci.org/sindresorhus/redent)
+
+> [Strip redundant indentation](https://github.com/sindresorhus/strip-indent) and [indent the string](https://github.com/sindresorhus/indent-string)
+
+
+## Install
+
+```
+$ npm install redent
+```
+
+
+## Usage
+
+```js
+const redent = require('redent');
+
+redent('\n  foo\n    bar\n', 1);
+//=> '\n foo\n   bar\n'
+```
+
+
+## API
+
+### redent(string, [count], [options])
+
+#### string
+
+Type: `string`
+
+The string to normalize indentation.
+
+#### count
+
+Type: `number`<br>
+Default: `0`
+
+How many times you want `options.indent` repeated.
+
+#### options
+
+Type: `object`
+
+##### indent
+
+Type: `string`<br>
+Default: `' '`
+
+The string to use for the indent.
+
+##### includeEmptyLines
+
+Type: `boolean`<br>
+Default: `false`
+
+Also indent empty lines.
+
+
+## License
+
+MIT © [Sindre Sorhus](https://sindresorhus.com)