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/extract-zip/index.d.ts

@@ -0,0 +1,21 @@
+// Based on the type definitions for extract-zip 1.6
+// Definitions by: Mizunashi Mana <https://github.com/mizunashi-mana>
+// Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped/blob/e69b58e/types/extract-zip/index.d.ts
+
+import { Entry, ZipFile } from 'yauzl';
+
+declare namespace extract {
+    interface Options {
+        dir: string;
+        defaultDirMode?: number;
+        defaultFileMode?: number;
+        onEntry?: (entry: Entry, zipfile: ZipFile) => void;
+    }
+}
+
+declare function extract(
+  zipPath: string,
+  opts: extract.Options,
+): Promise<void>;
+
+export = extract;