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/performance/NoAsyncChunksWarning.js

@@ -0,0 +1,21 @@
+/*
+	MIT License http://www.opensource.org/licenses/mit-license.php
+	Author Sean Larkin @thelarkinn
+*/
+
+"use strict";
+
+const WebpackError = require("../WebpackError");
+
+module.exports = class NoAsyncChunksWarning extends WebpackError {
+	constructor() {
+		super(
+			"webpack performance recommendations: \n" +
+				"You can limit the size of your bundles by using import() or require.ensure to lazy load some parts of your application.\n" +
+				"For more info visit https://webpack.js.org/guides/code-splitting/"
+		);
+
+		/** @type {string} */
+		this.name = "NoAsyncChunksWarning";
+	}
+};