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/Box/Box.js

@@ -0,0 +1,36 @@
+'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');
+var shallowEqual = require('reakit-utils/shallowEqual');
+
+// Automatically generated
+var BOX_KEYS = ["unstable_system"];
+
+var useBox = createHook.createHook({
+  name: "Box",
+  keys: BOX_KEYS,
+  propsAreEqual: function propsAreEqual(prev, next) {
+    var prevSystem = prev.unstable_system,
+        prevProps = _rollupPluginBabelHelpers._objectWithoutPropertiesLoose(prev, ["unstable_system"]);
+
+    var nextSystem = next.unstable_system,
+        nextProps = _rollupPluginBabelHelpers._objectWithoutPropertiesLoose(next, ["unstable_system"]);
+
+    if (prevSystem !== nextSystem && !shallowEqual.shallowEqual(prevSystem, nextSystem)) {
+      return false;
+    }
+
+    return shallowEqual.shallowEqual(prevProps, nextProps);
+  }
+});
+var Box = createComponent.createComponent({
+  as: "div",
+  useHook: useBox
+});
+
+exports.Box = Box;
+exports.useBox = useBox;