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/fast-glob/out/providers/sync.d.ts

@@ -0,0 +1,9 @@
+import { Task } from '../managers/tasks';
+import ReaderSync from '../readers/sync';
+import { Entry, EntryItem, ReaderOptions } from '../types';
+import Provider from './provider';
+export default class ProviderSync extends Provider<EntryItem[]> {
+    protected _reader: ReaderSync;
+    read(task: Task): EntryItem[];
+    api(root: string, task: Task, options: ReaderOptions): Entry[];
+}