Update main.html.erb

Author: lmrodriguezr

app/views/application/main.html.erb

@@ -1,3 +1,10 @@
+<div class="alert alert-info">
+  <h3>Maintenance 02/Dec/2025</h3>
+  The SeqCode Registry will undergo a service window on Tuesday, the 2nd
+  December, 2025 the entire day (CET). We apologize for any issues this may
+  cause.
+</div>
+
 <% if user_signed_in? %>
   <div id="notification-permission" class="text-center" style="display: none;">
     <%= button_tag(class: 'btn btn-primary', id: 'enable') do %>