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/string-width/readme.md

@@ -0,0 +1,50 @@
+# string-width
+
+> Get the visual width of a string - the number of columns required to display it
+
+Some Unicode characters are [fullwidth](https://en.wikipedia.org/wiki/Halfwidth_and_fullwidth_forms) and use double the normal width. [ANSI escape codes](https://en.wikipedia.org/wiki/ANSI_escape_code) are stripped and doesn't affect the width.
+
+Useful to be able to measure the actual width of command-line output.
+
+
+## Install
+
+```
+$ npm install string-width
+```
+
+
+## Usage
+
+```js
+const stringWidth = require('string-width');
+
+stringWidth('a');
+//=> 1
+
+stringWidth('古');
+//=> 2
+
+stringWidth('\u001B[1m古\u001B[22m');
+//=> 2
+```
+
+
+## Related
+
+- [string-width-cli](https://github.com/sindresorhus/string-width-cli) - CLI for this module
+- [string-length](https://github.com/sindresorhus/string-length) - Get the real length of a string
+- [widest-line](https://github.com/sindresorhus/widest-line) - Get the visual width of the widest line in a string
+
+
+---
+
+<div align="center">
+	<b>
+		<a href="https://tidelift.com/subscription/pkg/npm-string-width?utm_source=npm-string-width&utm_medium=referral&utm_campaign=readme">Get professional support for this package with a Tidelift subscription</a>
+	</b>
+	<br>
+	<sub>
+		Tidelift helps make open source sustainable for maintainers while giving companies<br>assurances about security, maintenance, and licensing for their dependencies.
+	</sub>
+</div>