Fix BuildError: nav links to renamed api_info endpoint

base.html referenced url_for('api_hello'), but that endpoint is now
api_info (/api/info). Since every page extends base.html, the dead
reference raised werkzeug BuildError and returned HTTP 500 site-wide --
including /finger/<user>, which federated Mastodon instances fetch for
link previews. The 500s also defeated nginx's 200-only cache, so every
fetch re-ran the finger subprocess against the daemon on mammut.

templates/base.html

@@ -33,7 +33,7 @@
                         <a class="nav-link" href="{{ url_for('finger') }}">Finger</a>
                     </li>
                     <li class="nav-item">
-                        <a class="nav-link" href="{{ url_for('api_hello') }}" target="_blank">API</a>
+                        <a class="nav-link" href="{{ url_for('api_info') }}" target="_blank">API</a>
                     </li>
                 </ul>
             </div>