Rename 'SANDS Portal' to 'Dashboard' in nav bar

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: JihaoXin

website/dashboard/templates/app.html

@@ -561,7 +561,7 @@
 
 <!-- NAV -->
 <nav id="main-nav" style="display:none">
-  <a class="nav-brand" href="{{ app_base }}/#" onclick="event.preventDefault();navigate('dashboard')"><span>ARK</span><span class="brand-suffix"> SANDS Portal</span></a>
+  <a class="nav-brand" href="{{ app_base }}/#" onclick="event.preventDefault();navigate('dashboard')"><span>ARK</span><span class="brand-suffix"> Dashboard</span></a>
   <span id="nav-admin-link" style="display:none"></span>
   <a href="{{ app_base }}/#feedback" onclick="event.preventDefault();navigate('feedback')"
      style="font-size:.85rem;font-weight:600;color:var(--text-second);text-decoration:none;padding:4px 10px;border-radius:6px;border:1px solid var(--border)">