fix: prevent stale voice sidebar after multi-session identity collision

When a second browser joins voice, LiveKit disconnects the first browser
via identity collision. The first browser's leaveVoice() was optimistically
removing the user from voiceUsers, but the user is still in voice from
the other session. Add handleForceDisconnect() that clears local connection
state without touching voiceUsers, keeping the sidebar accurate.

Also fix deploy.sh to clean up stale renamed containers from failed recreates.

deploy.sh

@@ -65,7 +65,8 @@ deploy() {
 
   # Rebuild
   echo "  [3/3] Building and restarting..."
-  ssh "$PI_USER@$host" "cd $path && docker compose up -d --build"
+  # Clean up stale renamed containers left by failed recreates (e.g. "d420a6c00439_backspace")
+  ssh "$PI_USER@$host" "cd $path && docker rm -f \$(docker ps -aq --filter 'name=_backspace' 2>/dev/null) 2>/dev/null; docker compose up -d --build"
 
   echo ""
   echo "  Done: $name"