sqlc: add CountTracksByAlbum and SearchTracks for Subsonic browse (#295)

CountTracksByAlbum drives the songCount attr on AlbumRef; SearchTracks
backs the song facet of search3.

internal/db/queries/tracks.sql

@@ -27,3 +27,12 @@ SELECT * FROM tracks WHERE file_path = $1;
 
 -- name: ListTracksByAlbum :many
 SELECT * FROM tracks WHERE album_id = $1 ORDER BY disc_number NULLS LAST, track_number NULLS LAST;
+
+-- name: CountTracksByAlbum :one
+SELECT count(*) FROM tracks WHERE album_id = $1;
+
+-- name: SearchTracks :many
+SELECT * FROM tracks
+WHERE title ILIKE '%' || $1 || '%'
+ORDER BY title
+LIMIT $2 OFFSET $3;