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/resolve/lib/caller.js

@@ -0,0 +1,12 @@
+'use strict';
+
+var $Error = require('es-errors');
+
+module.exports = function () {
+    // see https://code.google.com/p/v8/wiki/JavaScriptStackTraceApi
+    var origPrepareStackTrace = $Error.prepareStackTrace;
+    $Error.prepareStackTrace = function (_, stack) { return stack; };
+    var stack = (new $Error()).stack;
+    $Error.prepareStackTrace = origPrepareStackTrace;
+    return stack[2].getFileName();
+};