Add link previews, voice tiles and a menu volume slider; tidy the profile

- Link previews for web links in chat, fetched by the f0ckm upload host by
  default (linked sites never see the user's IP), or directly, or off
- Voice channel tiles above the chat on windows too narrow for the member list
- Per-person volume slider in the user context menu
- Profile panel: channel on its own line under the name, no Guest badge,
  voice actions moved to the context menu
- User information dialog refreshes every second
- Rate limiting mirrors Murmur's whole-second bucket leak, so irregular
  bursts are queued instead of dropped
- CHANGELOG.md

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/ui/Chat.svelte

@@ -2,9 +2,11 @@
   import Icon from './Icon.svelte';
   import ChatLog from './ChatLog.svelte';
   import Composer from './Composer.svelte';
+  import VoiceStage from './VoiceStage.svelte';
   import { session } from '../lib/session.svelte.ts';
 
-  let { onmenu, onpanel, showMenu }: { onmenu: () => void; onpanel: () => void; showMenu: boolean } = $props();
+  // showStage: voice tiles above the chat when the window is too narrow for the member list
+  let { onmenu, onpanel, showMenu, showStage = false }: { onmenu: () => void; onpanel: () => void; showMenu: boolean; showStage?: boolean } = $props();
 
   const isDm = $derived(session.view.startsWith('dm:'));
   const title = $derived(session.status === 'connected' ? session.viewTitle() : 'mumh5');
@@ -24,6 +26,8 @@
     <button class="icon-btn" onclick={onpanel} title="Members"><Icon name="users" /></button>
   </header>
 
+  {#if showStage && session.status === 'connected'}<VoiceStage />{/if}
+
   <ChatLog key={session.view}>
     {#snippet empty()}
       <div class="empty">