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/clipboard/karma.conf.js

@@ -0,0 +1,36 @@
+var webpackConfig = require('./webpack.config.js');
+
+module.exports = function (karma) {
+  karma.set({
+    plugins: [
+      'karma-webpack',
+      'karma-chai',
+      'karma-sinon',
+      'karma-mocha',
+      'karma-chrome-launcher',
+    ],
+
+    frameworks: ['chai', 'sinon', 'mocha', 'webpack'],
+
+    files: [
+      { pattern: 'src/**/*.js', watched: false },
+      { pattern: 'test/**/*.js', watched: false },
+    ],
+
+    preprocessors: {
+      'src/**/*.js': ['webpack'],
+      'test/**/*.js': ['webpack'],
+    },
+
+    webpack: {
+      module: webpackConfig.module,
+      plugins: webpackConfig.plugins,
+    },
+
+    webpackMiddleware: {
+      stats: 'errors-only',
+    },
+
+    browsers: ['ChromeHeadless'],
+  });
+};