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/@nodelib/fs.walk/out/readers/sync.d.ts

@@ -0,0 +1,15 @@
+import * as fsScandir from '@nodelib/fs.scandir';
+import type { Entry } from '../types';
+import Reader from './reader';
+export default class SyncReader extends Reader {
+    protected readonly _scandir: typeof fsScandir.scandirSync;
+    private readonly _storage;
+    private readonly _queue;
+    read(): Entry[];
+    private _pushToQueue;
+    private _handleQueue;
+    private _handleDirectory;
+    private _handleError;
+    private _handleEntry;
+    private _pushToStorage;
+}