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/webpack/lib/IgnoreErrorModuleFactory.js

@@ -0,0 +1,41 @@
+/*
+	MIT License http://www.opensource.org/licenses/mit-license.php
+	Author Ivan Kopeykin @vankop
+*/
+
+"use strict";
+
+const ModuleFactory = require("./ModuleFactory");
+
+/** @typedef {import("./ModuleFactory").ModuleFactoryCallback} ModuleFactoryCallback */
+/** @typedef {import("./ModuleFactory").ModuleFactoryCreateData} ModuleFactoryCreateData */
+/** @typedef {import("./NormalModuleFactory")} NormalModuleFactory */
+
+/**
+ * Ignores error when module is unresolved
+ */
+class IgnoreErrorModuleFactory extends ModuleFactory {
+	/**
+	 * Creates an instance of IgnoreErrorModuleFactory.
+	 * @param {NormalModuleFactory} normalModuleFactory normalModuleFactory instance
+	 */
+	constructor(normalModuleFactory) {
+		super();
+
+		this.normalModuleFactory = normalModuleFactory;
+	}
+
+	/**
+	 * Processes the provided data.
+	 * @param {ModuleFactoryCreateData} data data object
+	 * @param {ModuleFactoryCallback} callback callback
+	 * @returns {void}
+	 */
+	create(data, callback) {
+		this.normalModuleFactory.create(data, (err, result) =>
+			callback(null, result)
+		);
+	}
+}
+
+module.exports = IgnoreErrorModuleFactory;