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.scandir/out/index.d.ts

@@ -0,0 +1,12 @@
+import type { FileSystemAdapter, ReaddirAsynchronousMethod, ReaddirSynchronousMethod } from './adapters/fs';
+import * as async from './providers/async';
+import Settings, { Options } from './settings';
+import type { Dirent, Entry } from './types';
+declare type AsyncCallback = async.AsyncCallback;
+declare function scandir(path: string, callback: AsyncCallback): void;
+declare function scandir(path: string, optionsOrSettings: Options | Settings, callback: AsyncCallback): void;
+declare namespace scandir {
+    function __promisify__(path: string, optionsOrSettings?: Options | Settings): Promise<Entry[]>;
+}
+declare function scandirSync(path: string, optionsOrSettings?: Options | Settings): Entry[];
+export { scandir, scandirSync, Settings, AsyncCallback, Dirent, Entry, FileSystemAdapter, ReaddirAsynchronousMethod, ReaddirSynchronousMethod, Options };