Sign-in: stop telling a fast returning member off for being fast

The email-code endpoint refuses a request that arrives within two seconds of
the page loading, because a script fills a form instantly and a person does
not. A member whose email is already filled in by the browser has nothing to
type, taps straight away, and gets "Give the page a second, then tap again."

The page now waits out the remainder itself and sends when the window has
passed, so the person sees the normal sending state instead of an error.
The server check is untouched, so anything posting at the endpoint without a
page behind it still fails exactly as before.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

public/terms.html

@@ -37,7 +37,7 @@
     <p class="muted small" style="margin-top:18px">See also the <a href="/disclaimer">Disclaimer</a> and <a href="/privacy">Privacy Policy</a>.</p>
   </div>
 </div></section>
-<script src="/assets/common.js?v=20260916a"></script>
+<script src="/assets/common.js?v=20260923b"></script>
 <script src="/assets/legal.js?v=20260908a"></script>
 </body>
 </html>