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/detect-newline/index.d.ts

@@ -0,0 +1,26 @@
+declare const detectNewline: {
+	/**
+	Detect the dominant newline character of a string.
+
+	@returns The detected newline or `undefined` when no newline character is found.
+
+	@example
+	```
+	import detectNewline = require('detect-newline');
+
+	detectNewline('foo\nbar\nbaz\r\n');
+	//=> '\n'
+	```
+	*/
+	(string: string): '\r\n' | '\n' | undefined;
+
+	/**
+	Detect the dominant newline character of a string.
+
+	@returns The detected newline or `\n` when no newline character is found or the input is not a string.
+	*/
+	graceful(string: string): '\r\n' | '\n';
+	graceful(string?: unknown): '\n';
+};
+
+export = detectNewline;