feat(db/m7-coverage-gauge): GetAlbumCoverageRollup query

FILTER-aggregate count over albums.cover_art_source and albums.mbid
returning total, with_art, pending, settled, pending_no_mbid in a
single round-trip. Sub-millisecond on realistic libraries; no index
needed for v1. pending_no_mbid is a subset of pending — the UI
tooltip uses it to show how many "pending" rows are blocked on
missing MBID and won't be moved by another scan.

Also bumps the Makefile sqlc pin from 1.27.0 to 1.31.1 to match the
version that produced all existing committed dbq/*.go files. The
prior pin was stale; running make generate against 1.27.0 silently
rolled the codegen back (cosmetic version headers on most files
plus a real codegen shape change in DeleteArtistIfEmpty).

internal/db/dbq/albums.sql.go

@@ -121,6 +121,43 @@ func (q *Queries) GetAlbumByID(ctx context.Context, id pgtype.UUID) (Album, erro
 	return i, err
 }
 
+const getAlbumCoverageRollup = `-- name: GetAlbumCoverageRollup :one
+SELECT
+  COUNT(*)                                                                   AS total,
+  COUNT(*) FILTER (WHERE cover_art_source IN ('sidecar','embedded','mbcaa')) AS with_art,
+  COUNT(*) FILTER (WHERE cover_art_source IS NULL)                           AS pending,
+  COUNT(*) FILTER (WHERE cover_art_source = 'none')                          AS settled,
+  COUNT(*) FILTER (WHERE cover_art_source IS NULL AND mbid IS NULL)          AS pending_no_mbid
+FROM albums
+`
+
+type GetAlbumCoverageRollupRow struct {
+	Total         int64
+	WithArt       int64
+	Pending       int64
+	Settled       int64
+	PendingNoMbid int64
+}
+
+// M7 coverage-gauge: library-wide cover-art coverage rollup for the
+// admin gauge. Single sequential scan with FILTER aggregates —
+// sub-millisecond on realistic libraries. pending_no_mbid is a SUBSET
+// of pending; the UI surfaces it separately so operators can see how
+// many "pending" albums are blocked on missing MBID and won't be
+// helped by another scan.
+func (q *Queries) GetAlbumCoverageRollup(ctx context.Context) (GetAlbumCoverageRollupRow, error) {
+	row := q.db.QueryRow(ctx, getAlbumCoverageRollup)
+	var i GetAlbumCoverageRollupRow
+	err := row.Scan(
+		&i.Total,
+		&i.WithArt,
+		&i.Pending,
+		&i.Settled,
+		&i.PendingNoMbid,
+	)
+	return i, err
+}
+
 const listAlbumsAlphaByArtist = `-- name: ListAlbumsAlphaByArtist :many
 SELECT albums.id, albums.title, albums.sort_title, albums.artist_id, albums.release_date, albums.mbid, albums.cover_art_path, albums.created_at, albums.updated_at, albums.cover_art_source, artists.sort_name AS artist_sort_name
 FROM albums

internal/db/queries/albums.sql

@@ -124,3 +124,19 @@ SELECT a.id          AS album_id,
  WHERE a.mbid IS NULL
  ORDER BY a.created_at ASC
  LIMIT $1;
+
+-- name: GetAlbumCoverageRollup :one
+-- M7 coverage-gauge: library-wide cover-art coverage rollup for the
+-- admin gauge. Single sequential scan with FILTER aggregates —
+-- sub-millisecond on realistic libraries. pending_no_mbid is a SUBSET
+-- of pending; the UI surfaces it separately so operators can see how
+-- many "pending" albums are blocked on missing MBID and won't be
+-- helped by another scan.
+SELECT
+  COUNT(*)                                                                   AS total,
+  COUNT(*) FILTER (WHERE cover_art_source IN ('sidecar','embedded','mbcaa')) AS with_art,
+  COUNT(*) FILTER (WHERE cover_art_source IS NULL)                           AS pending,
+  COUNT(*) FILTER (WHERE cover_art_source = 'none')                          AS settled,
+  COUNT(*) FILTER (WHERE cover_art_source IS NULL AND mbid IS NULL)          AS pending_no_mbid
+FROM albums;
+