feat: add signup link

Author: jbriones1

public/frosh/2025/index.html

@@ -179,7 +179,13 @@ <h2>What's a "Frosh Week"?</h2>
             </p>
           </div>
           <div class="section-footer">
-            <a class="button bg-box" href="" target="_blank"> Sign up </a>
+            <a
+              class="button bg-box"
+              href="https://www.surveymonkey.ca/r/csssduckyfrosh2025"
+              target="_blank"
+            >
+              Sign up
+            </a>
             <a class="button bg-box" href="#faq">FAQ</a>
           </div>
         </div>