Fixes five queue bugs: Playlist relabel, last-track-empties, dormant-seed-from-player on first add, immediate panel reactivity, and front/back deque semantics. Adds JumpTo for row jumps.
Add a Queue toggle to the docked player bar opening a centered editable queue
overlay. New additive QueueService.ClearUpcoming keeps the playing track while
dropping the rest. Current track is non-removable.