Resolve "Verify maintenance mode with GraphQL / reimplement maintenance mode handling"

Closes #785 (closed)

aleksis/core/templates/core/partials/splash_screen.html

@@ -12,6 +12,13 @@
       This webbrowser doesn't support JavaScript, or its execution is blocked. Please use another browser to continue.
     {% endblocktrans %}
   </noscript>
+{% if maintenance_mode %}
+  <p>
+    {% blocktrans %}
+      The maintenance mode is currently enabled. Please try again later.
+    {% endblocktrans %}
+  </p>
+{% endif %}
 </div>
 <div class="lds-ellipsis">
   <div></div>
@@ -36,7 +43,7 @@
     max-height: calc(100vh - 10vh - calc(2 * min(85px, 15vh)));
   }
 
-  noscript {
+  noscript, p {
     font-family: Roboto, sans-serif;
     font-weight: 400;
   }