feat: soundboard, account menu, and call timer

Soundboard: the trigger travels over the WebSocket and every client in the
call plays the clip locally, instead of mixing it into the presser's
microphone or publishing a LiveKit track. No upstream bandwidth, no media
stack changes, and the clip is not degraded by voice processing.

Fan-out uses a new sendToRoomParticipants rather than sendToRoom: the latter
broadcasts a space room to the whole space, which is right for the presence
the sidebar shows and wrong for anything audible. The cooldown is enforced
server-side — a client-side one only slows down people not trying to abuse it,
and a soundboard is the easiest thing here to turn into a weapon. Playing is
open to anyone in the call; deciding what the buttons are needs MANAGE_SPACE.

Account menu: the name in the user bar had cursor-pointer and no handler, so
the interface was already promising a click that did nothing. Offers profile,
status and copy-id — not the Clips or account switching the reference design
shows, which would be dead UI here.

Call timer: startedAt comes from the server, so a late joiner sees the call's
age rather than their own arrival. Empty space rooms are destroyed already,
which is what makes the next call start from zero — no reset logic needed.

packages/web/src/components/voice/VoiceChannel.tsx

@@ -1,5 +1,6 @@
 import React, { useCallback, useMemo } from 'react';
 import { useVoiceStore } from '../../stores/voiceStore';
+import { CallTimer } from './CallTimer';
 import { useSpaceStore } from '../../stores/spaceStore';
 import { useAuthStore } from '../../stores/authStore';
 import { useContextMenuStore, type ContextMenuItem } from '../../stores/contextMenuStore';
@@ -33,6 +34,9 @@ interface VoiceChannelProps {
 
 /** Wrapper component for the volume slider so it can use hooks (useState). */
 export function VoiceChannel({ channelId, channelName, onClick, locked, canManage, onSettingsClick, voiceUserHandlers, dropZone }: VoiceChannelProps) {
+  // Present only while someone is in the channel; the server drops the room
+  // when it empties, which is what makes the next call start from zero.
+  const callStartedAt = useVoiceStore((s) => s.voiceRoomStarts.get(channelId));
   const serverVoiceUsers = useVoiceStore((s) => s.voiceUsers.get(channelId)) ?? EMPTY_VOICE_USERS;
   const currentVoiceChannel = useVoiceStore((s) => s.currentVoiceChannelId);
   const participants = useVoiceStore((s) => s.participants);
@@ -141,6 +145,12 @@ export function VoiceChannel({ channelId, channelName, onClick, locked, canManag
           </svg>
         )}
         <span className="truncate text-[15px] font-medium flex-1 text-left">{channelName}</span>
+        {callStartedAt !== undefined && (
+          <CallTimer
+            startedAt={callStartedAt}
+            className="flex-shrink-0 text-[11px] text-txt-tertiary font-medium"
+          />
+        )}
         {canManage && (
           <svg
             width="16"