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/@hapi/hoek/lib/bench.js

@@ -0,0 +1,29 @@
+'use strict';
+
+const internals = {};
+
+
+module.exports = internals.Bench = class {
+
+    constructor() {
+
+        this.ts = 0;
+        this.reset();
+    }
+
+    reset() {
+
+        this.ts = internals.Bench.now();
+    }
+
+    elapsed() {
+
+        return internals.Bench.now() - this.ts;
+    }
+
+    static now() {
+
+        const ts = process.hrtime();
+        return (ts[0] * 1e3) + (ts[1] / 1e6);
+    }
+};