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/regjsparser/README.md

@@ -0,0 +1,47 @@
+# RegJSParser
+
+Parsing the JavaScript's RegExp in JavaScript.
+
+## Installation
+
+```bash
+npm install regjsparser
+```
+
+## Usage
+
+```js
+var parse = require('regjsparser').parse;
+
+var parseTree = parse('^a'); // /^a/
+console.log(parseTree);
+
+// Toggle on/off additional features:
+var parseTree = parse('^a', '', {
+  // SEE: https://github.com/jviereck/regjsparser/pull/78
+  unicodePropertyEscape: true,
+
+  // SEE: https://github.com/jviereck/regjsparser/pull/83
+  namedGroups: true,
+
+  // SEE: https://github.com/jviereck/regjsparser/pull/89
+  lookbehind: true
+});
+console.log(parseTree);
+```
+
+## Testing
+
+To run the tests, run the following command:
+
+```bash
+npm test
+```
+
+To create a new reference file, execute…
+
+```bash
+node test/update-fixtures.js
+```
+
+…from the repo top directory.