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/enquirer/lib/theme.js

@@ -0,0 +1,11 @@
+'use strict';
+
+const styles = require('./styles');
+const symbols = require('./symbols');
+const utils = require('./utils');
+
+module.exports = prompt => {
+  prompt.options = utils.merge({}, prompt.options.theme, prompt.options);
+  prompt.symbols = symbols.merge(prompt.options);
+  prompt.styles = styles.merge(prompt.options);
+};