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/@emotion/cache/dist/declarations/src/index.d.ts

@@ -0,0 +1,16 @@
+import type { EmotionCache } from '@emotion/utils';
+import { StylisPlugin } from "./types.js";
+export interface Options {
+    nonce?: string;
+    stylisPlugins?: Array<StylisPlugin>;
+    key: string;
+    container?: Node;
+    speedy?: boolean;
+    /** @deprecate use `insertionPoint` instead */
+    prepend?: boolean;
+    insertionPoint?: HTMLElement;
+}
+declare let createCache: (options: Options) => EmotionCache;
+export default createCache;
+export type { EmotionCache };
+export type { StylisElement, StylisPlugin, StylisPluginCallback } from "./types.js";