feat: real-time user profile updates and propagate avatarColor to all Avatar callsites

Broadcast user_updated events over WebSocket when profile fields change,
updating members, DM participants, friends, and cached messages in real time.
Widen useVoiceParticipantMeta to return the full user object and add a
standalone avatarColor prop to Avatar so all ~16 callsites now resolve
the user's chosen gradient color instead of falling back to hash-based colors.

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

@@ -322,7 +322,7 @@ export function PictureInPicture() {
     [selectedStream, fallbackParticipant],
   );
 
-  const { displayName: resolvedName, avatar: resolvedAvatar } =
+  const { displayName: resolvedName, avatar: resolvedAvatar, user: resolvedUser } =
     useVoiceParticipantMeta(displayParticipant ?? EMPTY_PARTICIPANT);
 
   if (!shouldShow) return null;
@@ -370,6 +370,7 @@ export function PictureInPicture() {
                 name={resolvedName}
                 size={64}
                 userId={displayParticipant.homeUserId ?? displayParticipant.userId}
+                user={resolvedUser ?? undefined}
               />
               {speakingParticipantIds.has(displayParticipant.identity) && (
                 <div className="absolute -inset-1 rounded-full ring-2 ring-status-online animate-pulse" />