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/detect-libc/lib/process.js

@@ -0,0 +1,24 @@
+// Copyright 2017 Lovell Fuller and others.
+// SPDX-License-Identifier: Apache-2.0
+
+'use strict';
+
+const isLinux = () => process.platform === 'linux';
+
+let report = null;
+const getReport = () => {
+  if (!report) {
+    /* istanbul ignore next */
+    if (isLinux() && process.report) {
+      const orig = process.report.excludeNetwork;
+      process.report.excludeNetwork = true;
+      report = process.report.getReport();
+      process.report.excludeNetwork = orig;
+    } else {
+      report = {};
+    }
+  }
+  return report;
+};
+
+module.exports = { isLinux, getReport };