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/ajv-keywords/keywords/patternRequired.js

@@ -0,0 +1,21 @@
+'use strict';
+
+module.exports = function defFunc(ajv) {
+  defFunc.definition = {
+    type: 'object',
+    inline: require('./dotjs/patternRequired'),
+    statements: true,
+    errors: 'full',
+    metaSchema: {
+      type: 'array',
+      items: {
+        type: 'string',
+        format: 'regex'
+      },
+      uniqueItems: true
+    }
+  };
+
+  ajv.addKeyword('patternRequired', defFunc.definition);
+  return ajv;
+};