fix(db): drop redundant quarantine user index + tighten ListQuarantineForUser

- Composite PK (user_id, track_id) already serves WHERE user_id queries;
  the secondary (user_id, created_at DESC) index just amplified writes.
- ListQuarantineForUser now selects only the joined fields the SPA card
  actually renders (~10 columns) rather than embedding three full structs
  (~35 columns); halves wire/DB bandwidth before consumers exist.
- max(q.created_at)::timestamptz cast emits pgtype.Timestamptz instead of
  interface{} so handlers can read latest_at without a type-assert.

internal/db/queries/lidarr_quarantine.sql

@@ -17,13 +17,20 @@ DELETE FROM lidarr_quarantine
  RETURNING user_id, track_id, reason, notes, created_at;
 
 -- name: ListQuarantineForUser :many
--- Caller's own quarantines joined with track + album + artist for full
--- detail. Drives /library/hidden.
+-- Caller's own quarantines plus just the joined fields the SPA's
+-- /library/hidden actually renders. Embedding the full tracks/albums/artists
+-- structs would drag ~28 columns of file_path / sort_* / mbid / etc. that
+-- the row card never uses.
 SELECT
     sqlc.embed(q),
-    sqlc.embed(t),
-    sqlc.embed(al),
-    sqlc.embed(ar)
+    t.id          AS track_id_join,
+    t.title       AS track_title,
+    t.duration_ms AS track_duration_ms,
+    al.id         AS album_id,
+    al.title      AS album_title,
+    al.cover_art_path AS album_cover_art_path,
+    ar.id         AS artist_id,
+    ar.name       AS artist_name
 FROM lidarr_quarantine q
 JOIN tracks  t  ON t.id  = q.track_id
 JOIN albums  al ON al.id = t.album_id
@@ -42,8 +49,8 @@ SELECT
     al.title          AS album_title,
     al.id             AS album_id,
     al.mbid           AS lidarr_album_mbid,
-    count(q.user_id)::int AS report_count,
-    max(q.created_at)     AS latest_at
+    count(q.user_id)::int             AS report_count,
+    max(q.created_at)::timestamptz    AS latest_at
 FROM lidarr_quarantine q
 JOIN tracks  t  ON t.id  = q.track_id
 JOIN albums  al ON al.id = t.album_id