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/select/karma.conf.js

@@ -0,0 +1,23 @@
+module.exports = function(karma) {
+    karma.set({
+        plugins: ['karma-browserify', 'karma-chai', 'karma-mocha', 'karma-phantomjs-launcher'],
+
+        frameworks: ['browserify', 'chai', 'mocha'],
+
+        files: [
+            'src/**/*.js',
+            'test/**/*.js'
+        ],
+
+        preprocessors: {
+            'src/**/*.js' : ['browserify'],
+            'test/**/*.js': ['browserify']
+        },
+
+        browserify: {
+            debug: true
+        },
+
+        browsers: ['PhantomJS']
+    });
+}