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/node/NodeTargetPlugin.js

@@ -0,0 +1,103 @@
+/*
+	MIT License http://www.opensource.org/licenses/mit-license.php
+	Author Tobias Koppers @sokra
+*/
+
+"use strict";
+
+const ExternalsPlugin = require("../ExternalsPlugin");
+
+/** @typedef {import("../../declarations/WebpackOptions").ExternalsType} ExternalsType */
+/** @typedef {import("../Compiler")} Compiler */
+
+const builtins = [
+	"assert",
+	"assert/strict",
+	"async_hooks",
+	"buffer",
+	"child_process",
+	"cluster",
+	"console",
+	"constants",
+	"crypto",
+	"dgram",
+	"diagnostics_channel",
+	"dns",
+	"dns/promises",
+	"domain",
+	"events",
+	"fs",
+	"fs/promises",
+	"http",
+	"http2",
+	"https",
+	"inspector",
+	"inspector/promises",
+	"module",
+	"net",
+	"os",
+	"path",
+	"path/posix",
+	"path/win32",
+	"perf_hooks",
+	"process",
+	"punycode",
+	"querystring",
+	"readline",
+	"readline/promises",
+	"repl",
+	"stream",
+	"stream/consumers",
+	"stream/promises",
+	"stream/web",
+	"string_decoder",
+	"sys",
+	"timers",
+	"timers/promises",
+	"tls",
+	"trace_events",
+	"tty",
+	"url",
+	"util",
+	"util/types",
+	"v8",
+	"vm",
+	"wasi",
+	"worker_threads",
+	"zlib",
+	/^node:/,
+
+	// cspell:word pnpapi
+	// Yarn PnP adds pnpapi as "builtin"
+	"pnpapi"
+];
+
+class NodeTargetPlugin {
+	/**
+	 * Creates an instance of NodeTargetPlugin.
+	 * @param {ExternalsType} type default external type
+	 */
+	constructor(type = "node-commonjs") {
+		/** @type {ExternalsType} */
+		this.type = type;
+	}
+
+	/**
+	 * Applies the plugin by registering its hooks on the compiler.
+	 * @param {Compiler} compiler the compiler instance
+	 * @returns {void}
+	 */
+	apply(compiler) {
+		new ExternalsPlugin((dependency) => {
+			// When `require` node.js built-in modules with module output
+			// we should still emit `createRequire` for compatibility
+			if (dependency.category === "commonjs") {
+				return "node-commonjs";
+			}
+
+			return this.type;
+		}, builtins).apply(compiler);
+	}
+}
+
+module.exports = NodeTargetPlugin;