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/basic-ftp/dist/StringWriter.d.ts

@@ -0,0 +1,10 @@
+import { Writable } from "stream";
+import { StringEncoding } from "./StringEncoding";
+export declare class StringWriter extends Writable {
+    protected maxByteLength: number;
+    protected byteLength: number;
+    protected bufs: Buffer<ArrayBuffer>[];
+    constructor(maxByteLength?: number);
+    _write(chunk: Buffer | string | any, _: string, callback: (error: Error | null) => void): void;
+    getText(encoding: StringEncoding): string;
+}