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/EnvironmentNotSupportAsyncWarning.js

@@ -0,0 +1,51 @@
+/*
+	MIT License http://www.opensource.org/licenses/mit-license.php
+	Author Gengkun He @ahabhgk
+*/
+
+"use strict";
+
+const WebpackError = require("./WebpackError");
+const makeSerializable = require("./util/makeSerializable");
+
+/** @typedef {import("./Module")} Module */
+/** @typedef {import("./RuntimeTemplate")} RuntimeTemplate */
+/** @typedef {"asyncWebAssembly" | "topLevelAwait" | "external promise" | "external script" | "external import" | "external module"} Feature */
+
+class EnvironmentNotSupportAsyncWarning extends WebpackError {
+	/**
+	 * Creates an instance of EnvironmentNotSupportAsyncWarning.
+	 * @param {Module} module module
+	 * @param {Feature} feature feature
+	 */
+	constructor(module, feature) {
+		const message = `The generated code contains 'async/await' because this module is using "${feature}".
+However, your target environment does not appear to support 'async/await'.
+As a result, the code may not run as expected or may cause runtime errors.`;
+		super(message);
+
+		/** @type {string} */
+		this.name = "EnvironmentNotSupportAsyncWarning";
+		/** @type {Module} */
+		this.module = module;
+	}
+
+	/**
+	 * Creates an instance of EnvironmentNotSupportAsyncWarning.
+	 * @param {Module} module module
+	 * @param {RuntimeTemplate} runtimeTemplate compilation
+	 * @param {Feature} feature feature
+	 */
+	static check(module, runtimeTemplate, feature) {
+		if (!runtimeTemplate.supportsAsyncFunction()) {
+			module.addWarning(new EnvironmentNotSupportAsyncWarning(module, feature));
+		}
+	}
+}
+
+makeSerializable(
+	EnvironmentNotSupportAsyncWarning,
+	"webpack/lib/EnvironmentNotSupportAsyncWarning"
+);
+
+module.exports = EnvironmentNotSupportAsyncWarning;