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/xdg-basedir/index.d.ts

@@ -0,0 +1,81 @@
+declare const xdgBasedir: {
+	/**
+	Directory for user-specific data files.
+
+	@example
+	```js
+	import xdgBasedir = require('xdg-basedir');
+
+	xdgBasedir.data;
+	//=> '/home/sindresorhus/.local/share'
+	```
+	*/
+	readonly data?: string;
+
+	/**
+	Directory for user-specific configuration files.
+
+	@example
+	```js
+	import xdgBasedir = require('xdg-basedir');
+
+	xdgBasedir.config;
+	//=> '/home/sindresorhus/.config'
+	```
+	*/
+	readonly config?: string;
+
+	/**
+	Directory for user-specific non-essential data files.
+
+	@example
+	```js
+	import xdgBasedir = require('xdg-basedir');
+
+	xdgBasedir.cache;
+	//=> '/home/sindresorhus/.cache'
+	```
+	*/
+	readonly cache?: string;
+
+	/**
+	Directory for user-specific non-essential runtime files and other file objects (such as sockets, named pipes, etc).
+
+	@example
+	```js
+	import xdgBasedir = require('xdg-basedir');
+
+	xdgBasedir.runtime;
+	//=> '/run/user/sindresorhus'
+	```
+	*/
+	readonly runtime?: string;
+
+	/**
+	Preference-ordered array of base directories to search for data files in addition to `.data`.
+
+	@example
+	```js
+	import xdgBasedir = require('xdg-basedir');
+
+	xdgBasedir.dataDirs
+	//=> ['/home/sindresorhus/.local/share', '/usr/local/share/', '/usr/share/']
+	```
+	*/
+	readonly dataDirs: readonly string[];
+
+	/**
+	Preference-ordered array of base directories to search for configuration files in addition to `.config`.
+
+	@example
+	```js
+	import xdgBasedir = require('xdg-basedir');
+
+	xdgBasedir.configDirs;
+	//=> ['/home/sindresorhus/.config', '/etc/xdg']
+	```
+	*/
+	readonly configDirs: readonly string[];
+};
+
+export = xdgBasedir;