fix: Gitea homepage tile URLs — strip subdomain to get base domain

The JS was using `parts.length > 3` which only stripped the subdomain
for 4+ part hostnames. On gitea.fhirworx.io (3 parts), it kept the
full hostname as base, producing broken URLs like docs.gitea.fhirworx.io.

Fix: use parts.slice(-2) to always extract the last two segments as
the base domain (fhirworx.io).

infra/gitea/custom/templates/home.tmpl

@@ -291,7 +291,7 @@
 <script>
 (function() {
     var parts = location.hostname.split('.');
-    var base = parts.length > 3 ? parts.slice(1).join('.') : location.hostname;
+    var base = parts.length >= 3 ? parts.slice(-2).join('.') : location.hostname;
     document.querySelectorAll('.homelab-dashboard [data-subdomain]').forEach(function(el) {
         var sub = el.dataset.subdomain;
         var path = el.dataset.path || '';