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/eslint-plugin/configs/recommended.js

@@ -0,0 +1,68 @@
+/**
+ * External dependencies
+ */
+const { cosmiconfigSync } = require( 'cosmiconfig' );
+
+/**
+ * WordPress dependencies
+ */
+
+/**
+ * Internal dependencies
+ */
+const { isPackageInstalled } = require( '../utils' );
+
+const config = {
+	extends: [ require.resolve( './recommended-with-formatting.js' ) ],
+};
+
+if ( isPackageInstalled( 'prettier' ) ) {
+	config.extends.push( 'plugin:prettier/recommended' );
+
+	const { config: localPrettierConfig } =
+		cosmiconfigSync( 'prettier' ).search() || {};
+	const defaultPrettierConfig = require( '@wordpress/prettier-config' );
+	const prettierConfig = { ...defaultPrettierConfig, ...localPrettierConfig };
+	config.rules = {
+		'prettier/prettier': [ 'error', prettierConfig ],
+		// Prettier _disables_ this rule, but we want it!
+		// See https://github.com/prettier/eslint-config-prettier?tab=readme-ov-file#curly
+		// > This rule requires certain options.
+		// > …
+		// > If you like this rule, it can be used just fine with Prettier as long as you don’t use the "multi-line" or "multi-or-nest" option.
+		curly: [ 'error', 'all' ],
+	};
+}
+
+if ( isPackageInstalled( 'typescript' ) ) {
+	config.settings = {
+		'import/resolver': {
+			node: {
+				extensions: [ '.js', '.jsx', '.ts', '.tsx' ],
+			},
+		},
+	};
+	config.extends.push( 'plugin:@typescript-eslint/eslint-recommended' );
+	config.ignorePatterns = [ '**/*.d.ts' ];
+	config.plugins = [ '@typescript-eslint' ];
+	config.overrides = [
+		{
+			files: [ '**/*.ts', '**/*.tsx' ],
+			parser: '@typescript-eslint/parser',
+			rules: {
+				'no-duplicate-imports': 'off',
+				'import/no-duplicates': 'error',
+				// Don't require redundant JSDoc types in TypeScript files.
+				'jsdoc/require-param-type': 'off',
+				'jsdoc/require-returns-type': 'off',
+				// Handled by TS itself.
+				'no-unused-vars': 'off',
+				// no-shadow doesn't work correctly in TS, so let's use a TS-dedicated version instead.
+				'no-shadow': 'off',
+				'@typescript-eslint/no-shadow': 'error',
+			},
+		},
+	];
+}
+
+module.exports = config;