Fix HTML rendering for vendor notes links

Add proper HTML filtering to render mailto links and formatting in vendor notes.

- Create HtmlArraySerialized backend model to prevent HTML escaping
- Add filterOutputHtml() method to safely render HTML content
- Update template to use HTML filtering
- Decode HTML entities before display

Block/Adminhtml/Order/View/VendorNotes.php

@@ -6,23 +6,27 @@ use Magento\Sales\Model\Order;
 use Magento\Framework\App\Config\ScopeConfigInterface;
 use Magento\Store\Model\ScopeInterface;
 use Magento\Framework\Serialize\Serializer\Json;
+use Magento\Framework\Filter\Template as FilterTemplate;
 
 class VendorNotes extends Template
 {
     protected $_order;
     protected $_scopeConfig;
     protected $json;
+    protected $filterTemplate;
 
     public function __construct(
         \Magento\Backend\Block\Template\Context $context,
         \Magento\Sales\Model\Order $order,
         ScopeConfigInterface $scopeConfig,
         Json $json,
+        FilterTemplate $filterTemplate,
         array $data = []
     ) {
         $this->_order = $order;
         $this->_scopeConfig = $scopeConfig;
         $this->json = $json;
+        $this->filterTemplate = $filterTemplate;
         parent::__construct($context, $data);
     }