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/eslint/lib/cli-engine/formatters/jslint-xml.js

@@ -0,0 +1,41 @@
+/**
+ * @fileoverview JSLint XML reporter
+ * @author Ian Christian Myers
+ */
+"use strict";
+
+const xmlEscape = require("../xml-escape");
+
+//------------------------------------------------------------------------------
+// Public Interface
+//------------------------------------------------------------------------------
+
+module.exports = function(results) {
+
+    let output = "";
+
+    output += "<?xml version=\"1.0\" encoding=\"utf-8\"?>";
+    output += "<jslint>";
+
+    results.forEach(result => {
+        const messages = result.messages;
+
+        output += `<file name="${result.filePath}">`;
+
+        messages.forEach(message => {
+            output += [
+                `<issue line="${message.line}"`,
+                `char="${message.column}"`,
+                `evidence="${xmlEscape(message.source || "")}"`,
+                `reason="${xmlEscape(message.message || "")}${message.ruleId ? ` (${message.ruleId})` : ""}" />`
+            ].join(" ");
+        });
+
+        output += "</file>";
+
+    });
+
+    output += "</jslint>";
+
+    return output;
+};