feat(event_page.html): add check if event is in the past

home/templates/home/event_page.html

@@ -43,6 +43,10 @@
     <div class="p-4 bg-red-100 border-l-4 border-red-500 text-red-700">
       <p>{% trans "This event is fully booked. Please check back later for any cancellations." %}</p>
     </div>
+  {% elif page.start < now %}
+    <div class="p-4 bg-gray-100 border-l-4 border-gray-500 text-gray-700">
+      <p>{% trans "This event has already ended. Please check our calendar for upcoming events." %}</p>
+    </div>
   {% else %}
     <div class="p-4 bg-yellow-100 border-l-4 border-yellow-500 text-yellow-700">
       <p>{% trans "You are not signed up for this event. Please sign up to reserve your spot." %}</p>