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.stat/out/adapters/fs.d.ts

@@ -0,0 +1,13 @@
+/// <reference types="node" />
+import * as fs from 'fs';
+import type { ErrnoException } from '../types';
+export declare type StatAsynchronousMethod = (path: string, callback: (error: ErrnoException | null, stats: fs.Stats) => void) => void;
+export declare type StatSynchronousMethod = (path: string) => fs.Stats;
+export interface FileSystemAdapter {
+    lstat: StatAsynchronousMethod;
+    stat: StatAsynchronousMethod;
+    lstatSync: StatSynchronousMethod;
+    statSync: StatSynchronousMethod;
+}
+export declare const FILE_SYSTEM_ADAPTER: FileSystemAdapter;
+export declare function createFileSystemAdapter(fsMethods?: Partial<FileSystemAdapter>): FileSystemAdapter;