Store each client's play queue in the database

The queue lived in memory and was shared by all clients, so a restart or a
finished sync cleared it. Every client now has its own queue in the new
queue and queue_song tables (added to the undeployed migration 000006).

The music endpoints return the queue ID in the X-Queue-Id header and expect
it back. A request without an ID, or with an ended one, starts a new queue.
/music/reset ends the queue and returns a new ID, and a sync ends all
running queues. Ended queues are kept as history.

The deprecated legacy routes without the /api/v1 prefix are removed.

internal/server/library_handler.go

@@ -19,7 +19,7 @@ func (in *uuidInput) id() uuid.UUID {
 	return uuid.MustParse(in.UUID)
 }
 
-func (s *Server) registerLibrary(a apis) {
+func (s *Server) registerLibrary(a huma.API) {
 	l := s.library
 	op := func(id, path, summary, description string, errs ...int) huma.Operation {
 		return huma.Operation{