Add drag-and-drop reordering to the Queue sidebar: a per-row drag handle, a
floating drag ghost, and a drop indicator. When a QConnect transport is
connected the reorder is routed to the cloud (CtrlSrvrQueueReorderTracks) so
order stays WS-authoritative; otherwise it moves the local queue track via
core().move_track. The Flickable is non-interactive so a stale pressed_time
cannot strand the gesture and leave phantom scroll after release.
cc
vicrodh
5bc6552e98