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/stylelint/lib/utils/noFilesFoundError.js

@@ -0,0 +1,20 @@
+'use strict';
+
+class NoFilesFoundError extends Error {
+	/**
+	 * @param {string|string[]} fileList
+	 */
+	constructor(fileList) {
+		super();
+
+		if (typeof fileList === 'string') {
+			fileList = [fileList];
+		}
+
+		const pattern = fileList.filter((i) => !i.startsWith('!')).join(', ');
+
+		this.message = `No files matching the pattern "${pattern}" were found.`;
+	}
+}
+
+module.exports = NoFilesFoundError;