feat(subsonic): getAlbumList2 recent and frequent read the caller's play history (#6293)

type=recent orders the caller's albums by their latest play (skips
included); type=frequent orders them by completed plays (skips
excluded). Plays of tracks whose file is gone do not count, and both
page by size/offset like the other types.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/db/queries/albums.sql

@@ -99,6 +99,56 @@ WHERE EXISTS (
 ORDER BY albums.sort_title, albums.id
 LIMIT sqlc.arg(lim) OFFSET sqlc.arg(off);
 
+-- name: ListAlbumsRecentlyPlayedByUser :many
+-- The user's albums, most recently played first: an album's time is its
+-- latest play of any of its tracks, skips included, since a skip is still
+-- the user reaching for that album. Plays of tracks whose file is gone do
+-- not count. Serves Subsonic getAlbumList2?type=recent.
+--
+-- Aggregates play_events per track first (play_events_user_track_idx), then
+-- folds tracks into albums, so the join runs over distinct tracks rather
+-- than every play.
+WITH plays AS (
+    SELECT track_id, max(started_at) AS last_played
+    FROM play_events
+    WHERE user_id = sqlc.arg(user_id)
+    GROUP BY track_id
+), per_album AS (
+    SELECT t.album_id, max(p.last_played) AS last_played
+    FROM plays p
+    JOIN tracks t ON t.id = p.track_id
+    WHERE t.missing_since IS NULL
+    GROUP BY t.album_id
+)
+SELECT albums.*
+FROM per_album pa
+JOIN albums ON albums.id = pa.album_id
+ORDER BY pa.last_played DESC, albums.id
+LIMIT sqlc.arg(lim) OFFSET sqlc.arg(off);
+
+-- name: ListAlbumsFrequentlyPlayedByUser :many
+-- The user's albums, most played first: an album's count is the user's
+-- completed plays across its tracks. Skips do not count, so skipping
+-- through an album does not make it a favourite. Plays of tracks whose file
+-- is gone do not count. Serves Subsonic getAlbumList2?type=frequent.
+WITH plays AS (
+    SELECT track_id, count(*) AS cnt
+    FROM play_events
+    WHERE user_id = sqlc.arg(user_id) AND was_skipped = false
+    GROUP BY track_id
+), per_album AS (
+    SELECT t.album_id, sum(p.cnt) AS cnt
+    FROM plays p
+    JOIN tracks t ON t.id = p.track_id
+    WHERE t.missing_since IS NULL
+    GROUP BY t.album_id
+)
+SELECT albums.*
+FROM per_album pa
+JOIN albums ON albums.id = pa.album_id
+ORDER BY pa.cnt DESC, albums.id
+LIMIT sqlc.arg(lim) OFFSET sqlc.arg(off);
+
 -- name: SearchAlbums :many
 SELECT * FROM albums
 WHERE title ILIKE '%' || $1 || '%'