Homepage: move File upload + Notifications to top area; sidebar: add Get App below Settings

Top area now holds Users/Businesses/Bots/Notifications/File upload; manage area is
Network/Settings; external area is Get SimpleX App. Add a padded Get App link
(nav-sep) below Settings in the sidebar.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

manager/templates/base.html

@@ -277,6 +277,7 @@
       <a href="https://simplex.chat/file/" target="_blank" rel="noopener"><span class="ico">📁</span><span class="lbl">File upload</span></a>
       <a href="/notifications" class="nav-sep {% if nav_active == 'notifications' %}active{% endif %}"><span class="ico">🔔</span><span class="lbl">Notifications</span><span class="notif-badge" id="notif-badge" style="display:none;"></span></a>
       <a href="/settings" class="nav-sep {% if nav_active == 'settings' %}active{% endif %}"><span class="ico">⚙️</span><span class="lbl">Settings</span></a>
+      <a href="https://simplex.chat/downloads/" target="_blank" rel="noopener" class="nav-sep"><span class="ico">📲</span><span class="lbl">Get App</span></a>
     </nav>
     <div class="side-foot">
       <a href="/network" class="side-status" id="side-status" title="View SimpleX network &amp; servers"