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/@wordpress/components/build-module/composite/index.js

@@ -0,0 +1,17 @@
+/**
+ * Composite is a component that may contain navigable items represented by
+ * CompositeItem. It's inspired by the WAI-ARIA Composite Role and implements
+ * all the keyboard navigation mechanisms to ensure that there's only one
+ * tab stop for the whole Composite element. This means that it can behave as
+ * a roving tabindex or aria-activedescendant container.
+ *
+ * @see https://reakit.io/docs/composite/
+ *
+ * The plan is to build own API that accounts for future breaking changes
+ * in Reakit (https://github.com/WordPress/gutenberg/pull/28085).
+ */
+/* eslint-disable-next-line no-restricted-imports */
+export { Composite, CompositeGroup, CompositeItem, useCompositeState } from 'reakit';
+
+/* eslint-disable-next-line no-restricted-imports */
+//# sourceMappingURL=index.js.map