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/acorn-import-phases/README.md

@@ -0,0 +1,30 @@
+# Support for `import defer` and `import souce` in acorn
+
+## Install
+
+```
+npm install acorn-import-phases
+```
+
+## Usage
+
+This module provides a plugin that can be used to extend the Acorn Parser class:
+
+```js
+const {Parser} = require('acorn');
+const importPhases = require('acorn-import-phases');
+Parser.extend(importPhases()).parse('...');
+```
+
+By default, the plugin supports both `import defer` and `import source` syntax. You can disable one of them by passing an options object:
+
+```js
+const {Parser} = require('acorn');
+const importPhases = require('acorn-import-phases');
+Parser.extend(importPhases({ defer: false })).parse('...');
+Parser.extend(importPhases({ source: false })).parse('...');
+```
+
+## License
+
+This plugin is released under an MIT License.