Add hard-coded notification with gift code for Hetzner Cloud

Author: rudis

src/ctf_gameserver/web/registration/templates/team_downloads.html

@@ -6,6 +6,12 @@
     <h1>{% block title %}{% trans 'Downloads' %}{% endblock %}</h1>
 </div>
 
+<div class="alert alert-primary" role="alert">
+    Our infra sponsor Hetzner sends a gift to all participating teams from FAUST CTF 2025. Use the code <code>HetznerXFAUSTCTF25</code> to get 10€ for Hetzner Cloud. You can use this code to host your vulnbox or try out Hetzner on your own. <br>
+
+    The code can be activated until 30th of September. After activation, the voucher amount will be available for three months. Only applicable to new accounts. It can be used 600 times in total.
+</div>
+
 <p class="lead">
     {% blocktrans %}
     These files are provided to your team personally.