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/rxjs/src/internal/operators/concat.ts

@@ -0,0 +1,22 @@
+import { ObservableInputTuple, OperatorFunction, SchedulerLike } from '../types';
+import { operate } from '../util/lift';
+import { concatAll } from './concatAll';
+import { popScheduler } from '../util/args';
+import { from } from '../observable/from';
+
+/** @deprecated Replaced with {@link concatWith}. Will be removed in v8. */
+export function concat<T, A extends readonly unknown[]>(...sources: [...ObservableInputTuple<A>]): OperatorFunction<T, T | A[number]>;
+/** @deprecated Replaced with {@link concatWith}. Will be removed in v8. */
+export function concat<T, A extends readonly unknown[]>(
+  ...sourcesAndScheduler: [...ObservableInputTuple<A>, SchedulerLike]
+): OperatorFunction<T, T | A[number]>;
+
+/**
+ * @deprecated Replaced with {@link concatWith}. Will be removed in v8.
+ */
+export function concat<T, R>(...args: any[]): OperatorFunction<T, R> {
+  const scheduler = popScheduler(args);
+  return operate((source, subscriber) => {
+    concatAll()(from([source, ...args], scheduler)).subscribe(subscriber);
+  });
+}