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/cache/AddBuildDependenciesPlugin.js

@@ -0,0 +1,33 @@
+/*
+	MIT License http://www.opensource.org/licenses/mit-license.php
+	Author Tobias Koppers @sokra
+*/
+
+"use strict";
+
+/** @typedef {import("../Compiler")} Compiler */
+
+const PLUGIN_NAME = "AddBuildDependenciesPlugin";
+
+class AddBuildDependenciesPlugin {
+	/**
+	 * Creates an instance of AddBuildDependenciesPlugin.
+	 * @param {Iterable<string>} buildDependencies list of build dependencies
+	 */
+	constructor(buildDependencies) {
+		this.buildDependencies = new Set(buildDependencies);
+	}
+
+	/**
+	 * Applies the plugin by registering its hooks on the compiler.
+	 * @param {Compiler} compiler the compiler instance
+	 * @returns {void}
+	 */
+	apply(compiler) {
+		compiler.hooks.compilation.tap(PLUGIN_NAME, (compilation) => {
+			compilation.buildDependencies.addAll(this.buildDependencies);
+		});
+	}
+}
+
+module.exports = AddBuildDependenciesPlugin;