improved library scan speeds, added library manager component

-libraries tab now opens a library manager
-choose library directory, manually soft scan and rescan
-batched db queues
-mp3 header-based duration extraction

backend/database/sql/queries/artist_credit_artists.sql

@@ -15,3 +15,6 @@ WHERE id =?;
 DELETE FROM artist_credit_artist 
 WHERE id =?;
 
+-- name: DeleteAllArtistCreditArtists :exec
+DELETE FROM artist_credit_artist;
+