redesign: 2-col layout, peers in sidebar, IRC-style messages, NAT dot

- Peers moved from right panel into sidebar below Rooms
- Messages left-aligned IRC style: time · alias · text
- Per-peer colored dot: green=direct/NAT-punched, amber=relay/connecting, red=failed
- Hover title on peer row shows full ID, connection type, remote address, last seen
- Removed right PeerList panel

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

web/src/pages/Chat.tsx

@@ -1,13 +1,11 @@
 import { Sidebar } from '../components/Sidebar'
 import { MessagePane } from '../components/MessagePane'
-import { PeerList } from '../components/PeerList'
 
 export function Chat() {
   return (
     <div className="chat-layout">
       <Sidebar />
       <MessagePane />
-      <PeerList />
     </div>
   )
 }