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/trim-newlines/index.d.ts

@@ -0,0 +1,42 @@
+declare const trimNewlines: {
+	/**
+	Trim from the start and end of a string.
+
+	@example
+	```js
+	import trimNewlines = require('trim-newlines');
+
+	trimNewlines('\n🦄\r\n');
+	//=> '🦄'
+	```
+	*/
+	(string: string): string;
+
+	/**
+	Trim from the start of a string.
+
+	@example
+	```js
+	import trimNewlines = require('trim-newlines');
+
+	trimNewlines.start('\n🦄\r\n');
+	//=> '🦄\r\n'
+	```
+	*/
+	start(string: string): string;
+
+	/**
+	Trim from the end of a string.
+
+	@example
+	```js
+	import trimNewlines = require('trim-newlines');
+
+	trimNewlines.end('\n🦄\r\n');
+	//=> '\n🦄'
+	```
+	*/
+	end(string: string): string;
+};
+
+export = trimNewlines;