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/settings.d.ts

@@ -0,0 +1,20 @@
+import * as fsStat from '@nodelib/fs.stat';
+import * as fs from './adapters/fs';
+export interface Options {
+    followSymbolicLinks?: boolean;
+    fs?: Partial<fs.FileSystemAdapter>;
+    pathSegmentSeparator?: string;
+    stats?: boolean;
+    throwErrorOnBrokenSymbolicLink?: boolean;
+}
+export default class Settings {
+    private readonly _options;
+    readonly followSymbolicLinks: boolean;
+    readonly fs: fs.FileSystemAdapter;
+    readonly pathSegmentSeparator: string;
+    readonly stats: boolean;
+    readonly throwErrorOnBrokenSymbolicLink: boolean;
+    readonly fsStatSettings: fsStat.Settings;
+    constructor(_options?: Options);
+    private _getValue;
+}