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/hmr/HotModuleReplacementRuntimeModule.js

@@ -0,0 +1,43 @@
+/*
+	MIT License http://www.opensource.org/licenses/mit-license.php
+	Author Tobias Koppers @sokra
+*/
+
+"use strict";
+
+const RuntimeGlobals = require("../RuntimeGlobals");
+const RuntimeModule = require("../RuntimeModule");
+const Template = require("../Template");
+
+class HotModuleReplacementRuntimeModule extends RuntimeModule {
+	constructor() {
+		super("hot module replacement", RuntimeModule.STAGE_BASIC);
+	}
+
+	/**
+	 * Generates runtime code for this runtime module.
+	 * @returns {string | null} runtime code
+	 */
+	generate() {
+		return Template.getFunctionContent(
+			require("./HotModuleReplacement.runtime")
+		)
+			.replace(
+				/\$interceptModuleExecution\$/g,
+				RuntimeGlobals.interceptModuleExecution
+			)
+			.replace(/\$moduleCache\$/g, RuntimeGlobals.moduleCache)
+			.replace(/\$hmrModuleData\$/g, RuntimeGlobals.hmrModuleData)
+			.replace(/\$hmrDownloadManifest\$/g, RuntimeGlobals.hmrDownloadManifest)
+			.replace(
+				/\$hmrInvalidateModuleHandlers\$/g,
+				RuntimeGlobals.hmrInvalidateModuleHandlers
+			)
+			.replace(
+				/\$hmrDownloadUpdateHandlers\$/g,
+				RuntimeGlobals.hmrDownloadUpdateHandlers
+			);
+	}
+}
+
+module.exports = HotModuleReplacementRuntimeModule;