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/private-apis.js

@@ -0,0 +1,43 @@
+/**
+ * WordPress dependencies
+ */
+
+/**
+ * Internal dependencies
+ */
+import { Composite as CompositeV2, CompositeGroup as CompositeGroupV2, CompositeItem as CompositeItemV2, CompositeRow as CompositeRowV2, useCompositeStore as useCompositeStoreV2 } from './composite/v2';
+import { default as CustomSelectControl } from './custom-select-control';
+import { positionToPlacement as __experimentalPopoverLegacyPositionToPlacement } from './popover/utils';
+import { default as ProgressBar } from './progress-bar';
+import { createPrivateSlotFill } from './slot-fill';
+import { DropdownMenu as DropdownMenuV2, DropdownMenuGroup as DropdownMenuGroupV2, DropdownMenuItem as DropdownMenuItemV2, DropdownMenuCheckboxItem as DropdownMenuCheckboxItemV2, DropdownMenuRadioItem as DropdownMenuRadioItemV2, DropdownMenuSeparator as DropdownMenuSeparatorV2, DropdownMenuItemLabel as DropdownMenuItemLabelV2, DropdownMenuItemHelpText as DropdownMenuItemHelpTextV2 } from './dropdown-menu-v2';
+import { ComponentsContext } from './context/context-system-provider';
+import Theme from './theme';
+import Tabs from './tabs';
+import { kebabCase } from './utils/strings';
+import { lock } from './lock-unlock';
+export const privateApis = {};
+lock(privateApis, {
+  CompositeV2,
+  CompositeGroupV2,
+  CompositeItemV2,
+  CompositeRowV2,
+  useCompositeStoreV2,
+  CustomSelectControl,
+  __experimentalPopoverLegacyPositionToPlacement,
+  createPrivateSlotFill,
+  ComponentsContext,
+  ProgressBar,
+  Tabs,
+  Theme,
+  DropdownMenuV2,
+  DropdownMenuGroupV2,
+  DropdownMenuItemV2,
+  DropdownMenuCheckboxItemV2,
+  DropdownMenuRadioItemV2,
+  DropdownMenuSeparatorV2,
+  DropdownMenuItemLabelV2,
+  DropdownMenuItemHelpTextV2,
+  kebabCase
+});
+//# sourceMappingURL=private-apis.js.map