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/dependencies/ModuleHotAcceptDependency.js

@@ -0,0 +1,42 @@
+/*
+	MIT License http://www.opensource.org/licenses/mit-license.php
+	Author Tobias Koppers @sokra
+*/
+
+"use strict";
+
+const makeSerializable = require("../util/makeSerializable");
+const ModuleDependency = require("./ModuleDependency");
+const ModuleDependencyTemplateAsId = require("./ModuleDependencyTemplateAsId");
+
+/** @typedef {import("../javascript/JavascriptParser").Range} Range */
+
+class ModuleHotAcceptDependency extends ModuleDependency {
+	/**
+	 * Creates an instance of ModuleHotAcceptDependency.
+	 * @param {string} request the request string
+	 * @param {Range} range location in source code
+	 */
+	constructor(request, range) {
+		super(request, Infinity);
+		this.range = range;
+		this.weak = true;
+	}
+
+	get type() {
+		return "module.hot.accept";
+	}
+
+	get category() {
+		return "commonjs";
+	}
+}
+
+makeSerializable(
+	ModuleHotAcceptDependency,
+	"webpack/lib/dependencies/ModuleHotAcceptDependency"
+);
+
+ModuleHotAcceptDependency.Template = ModuleDependencyTemplateAsId;
+
+module.exports = ModuleHotAcceptDependency;