appview/pages: add agreement to tos/privacy in signup

Just legal CYA since we previously didn't have an explicit line stating
agreement & linking to the terms anywhere.

Signed-off-by: Anirudh Oppiliappan <[e-mail]>

appview/pages/templates/user/signup.html

···
                 </p>
 
                 <p id="signup-msg" class="error w-full"></p>
+                <p class="text-sm text-gray-500 pt-4">
+                  By signing up, you agree to our <a href="/terms" class="underline">Terms of Service</a> and <a href="/privacy" class="underline">Privacy Policy</a>.
+                </p>
             </main>
         </body>
     </html>