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/jsx-ast-utils/src/index.js

@@ -0,0 +1,19 @@
+import hasProp, { hasAnyProp, hasEveryProp } from './hasProp';
+import elementType from './elementType';
+import eventHandlers, { eventHandlersByType } from './eventHandlers';
+import getProp from './getProp';
+import getPropValue, { getLiteralPropValue } from './getPropValue';
+import propName from './propName';
+
+module.exports = {
+  hasProp,
+  hasAnyProp,
+  hasEveryProp,
+  elementType,
+  eventHandlers,
+  eventHandlersByType,
+  getProp,
+  getPropValue,
+  getLiteralPropValue,
+  propName,
+};