feat: add channel list with DM user names and fix message scroll behavior

- Add get_other_dm_user method to ChannelMemberService to retrieve the other participant in a DM channel
- Update WebView to display DM partner's nickname instead of channel label in sidebar
- Change sidebar links to use channel uid and name from the new channel list structure
- Fix message offset query to silently handle errors instead of crashing
- Replace scroll-to-bottom with scrollIntoView on last message for smoother UX
- Increase initial layout update delay from 200ms to 1000ms for better timing

src/snek/templates/app.html

@@ -34,7 +34,7 @@
       <h2 class="no-select">Chat Rooms</h2>
       <ul>
         {% for channel in channels %}
-        <li><a class="no-select" href="/web/{{channel['channel_uid']}}.html">{{channel['label']}}</a></li>
+        <li><a class="no-select" href="/channel/{{channel['uid']}}.html">{{channel['name']}}</a></li>
         {% endfor %}
       </ul>
     </aside>