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/scripts/config/babel-transform.js

@@ -0,0 +1,11 @@
+/**
+ * External dependencies
+ */
+const babelJest = require( 'babel-jest' );
+
+// Remove this workaround when https://github.com/facebook/jest/issues/11444 gets resolved in Jest.
+const babelJestInterop = babelJest.__esModule ? babelJest.default : babelJest;
+
+module.exports = babelJestInterop.createTransformer( {
+	presets: [ '@wordpress/babel-preset-default' ],
+} );