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/.eslintrc.js

@@ -0,0 +1,27 @@
+/**
+ * Internal dependencies
+ */
+const { hasBabelConfig } = require( '../utils' );
+
+const eslintConfig = {
+	root: true,
+	extends: [ 'plugin:@wordpress/eslint-plugin/recommended' ],
+	overrides: [
+		{
+			// Unit test files and their helpers only.
+			files: [ '**/@(test|__tests__)/**/*.js', '**/?(*.)test.js' ],
+			extends: [ 'plugin:@wordpress/eslint-plugin/test-unit' ],
+		},
+	],
+};
+
+if ( ! hasBabelConfig() ) {
+	eslintConfig.parserOptions = {
+		requireConfigFile: false,
+		babelOptions: {
+			presets: [ require.resolve( '@wordpress/babel-preset-default' ) ],
+		},
+	};
+}
+
+module.exports = eslintConfig;