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/e2e-test-utils-playwright/build/request-utils/preferences.js

@@ -0,0 +1,21 @@
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.resetPreferences = void 0;
+/**
+ * Reset user preferences
+ *
+ * @param this Request utils.
+ */
+async function resetPreferences() {
+    await this.rest({
+        path: '/wp/v2/users/me',
+        method: 'PUT',
+        data: {
+            meta: {
+                persisted_preferences: {},
+            },
+        },
+    });
+}
+exports.resetPreferences = resetPreferences;
+//# sourceMappingURL=preferences.js.map