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/enhanced-resolve/lib/util/process-browser.js

@@ -0,0 +1,23 @@
+/*
+	MIT License http://www.opensource.org/licenses/mit-license.php
+	Author Tobias Koppers @sokra
+*/
+
+"use strict";
+
+module.exports = {
+	/**
+	 * @type {Record<string, string>}
+	 */
+	versions: {},
+	// eslint-disable-next-line jsdoc/reject-function-type
+	/** @param {Function} fn function */
+	nextTick(fn) {
+		// eslint-disable-next-line prefer-rest-params
+		const args = Array.prototype.slice.call(arguments, 1);
+		Promise.resolve().then(() => {
+			// eslint-disable-next-line prefer-spread
+			fn.apply(null, args);
+		});
+	},
+};