fix: extract only hostname for favicon data-domain

data-domain was set to the full result URL (https://en.wikipedia.org/...).
This caused /favicon/ to receive malformed domain strings.

Now extracts u.Hostname() in FromResponse and passes it as Domain
to result_item.html.

internal/views/templates/result_item.html

@@ -4,7 +4,7 @@
     <a href="{{.URL}}" target="_blank" rel="noopener noreferrer">{{.SafeTitle}}</a>
   </div>
   <div class="result_url">
-    <img class="result-favicon" data-domain="{{.URL}}" src="" alt="" loading="lazy" style="display:none">
+    <img class="result-favicon" data-domain="{{.Domain}}" src="" alt="" loading="lazy" style="display:none">
     <a href="{{.URL}}" target="_blank" rel="noopener noreferrer">{{.URL}}</a>
     <span class="engine-badge" data-engine="{{.Engine}}">{{.Engine}}</span>
   </div>