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/reakit/lib/Grid/GridRow.js

@@ -0,0 +1,37 @@
+'use strict';
+
+Object.defineProperty(exports, '__esModule', { value: true });
+
+var _rollupPluginBabelHelpers = require('../_rollupPluginBabelHelpers-8f9a8751.js');
+var createComponent = require('reakit-system/createComponent');
+var createHook = require('reakit-system/createHook');
+require('reakit-utils/shallowEqual');
+require('react');
+require('reakit-utils/useForkRef');
+require('reakit-utils/useIsomorphicEffect');
+require('../Role/Role.js');
+require('../findEnabledItemById-03112678.js');
+require('../__keys-3b597476.js');
+require('../Id/IdProvider.js');
+require('../Id/Id.js');
+var __keys = require('../__keys-d2d383f0.js');
+require('../Group/Group.js');
+var Composite_CompositeGroup = require('../Composite/CompositeGroup.js');
+
+var unstable_useGridRow = createHook.createHook({
+  name: "GridRow",
+  compose: Composite_CompositeGroup.useCompositeGroup,
+  keys: __keys.GRID_ROW_KEYS,
+  useProps: function useProps(_, htmlProps) {
+    return _rollupPluginBabelHelpers._objectSpread2({
+      role: "row"
+    }, htmlProps);
+  }
+});
+var unstable_GridRow = createComponent.createComponent({
+  as: "div",
+  useHook: unstable_useGridRow
+});
+
+exports.unstable_GridRow = unstable_GridRow;
+exports.unstable_useGridRow = unstable_useGridRow;