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/JavascriptHotModuleReplacementHelper.js

@@ -0,0 +1,38 @@
+/*
+	MIT License http://www.opensource.org/licenses/mit-license.php
+	Author Haijie Xie @hai-x
+*/
+
+"use strict";
+
+const RuntimeGlobals = require("../RuntimeGlobals");
+
+const Template = require("../Template");
+
+/**
+ * Generates javascript hmr.
+ * @param {string} type unique identifier used for HMR runtime properties
+ * @returns {string} HMR runtime code
+ */
+const generateJavascriptHMR = (type) =>
+	Template.getFunctionContent(
+		require("../hmr/JavascriptHotModuleReplacement.runtime")
+	)
+		.replace(/\$key\$/g, type)
+		.replace(/\$installedChunks\$/g, "installedChunks")
+		.replace(/\$loadUpdateChunk\$/g, "loadUpdateChunk")
+		.replace(/\$moduleCache\$/g, RuntimeGlobals.moduleCache)
+		.replace(/\$moduleFactories\$/g, RuntimeGlobals.moduleFactories)
+		.replace(/\$ensureChunkHandlers\$/g, RuntimeGlobals.ensureChunkHandlers)
+		.replace(/\$hasOwnProperty\$/g, RuntimeGlobals.hasOwnProperty)
+		.replace(/\$hmrModuleData\$/g, RuntimeGlobals.hmrModuleData)
+		.replace(
+			/\$hmrDownloadUpdateHandlers\$/g,
+			RuntimeGlobals.hmrDownloadUpdateHandlers
+		)
+		.replace(
+			/\$hmrInvalidateModuleHandlers\$/g,
+			RuntimeGlobals.hmrInvalidateModuleHandlers
+		);
+
+module.exports.generateJavascriptHMR = generateJavascriptHMR;