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/server.go

@@ -68,8 +68,11 @@ func New(cfg config.Config, q repository.Querier, database Database) (*Server, e
 
 // afterSync refreshes cached data once a sync has finished.
 func (s *Server) afterSync(ctx context.Context) {
-	if err := s.music.Reset(ctx); err != nil {
-		logging.GetLogger().Error("Failed to reset music after sync", zap.Error(err))
+	if err := s.music.EndAllQueues(ctx); err != nil {
+		logging.GetLogger().Error("Failed to end the queues after sync", zap.Error(err))
+	}
+	if err := s.music.ReloadSoundtracks(ctx); err != nil {
+		logging.GetLogger().Error("Failed to reload soundtracks after sync", zap.Error(err))
 	}
 	if err := s.search.Reload(ctx); err != nil {
 		logging.GetLogger().Error("Failed to reload search cache after sync", zap.Error(err))