feat(database): shape the library like files, and shrink the catalog

Plans 013 and 014, the album page that prompted them, and the smaller
fixes they turned up. Changelog, largest first.

## The local library is shaped like files, not like MusicBrainz

`audio_files` carries its own tags and points at `albums` and
`artists`; `file_genres` is the one real many-to-many. `recordings`,
`release_group_recordings`, `artist_credit`, `artist_credit_artist`,
`recording_genres`, `release_groups` and `release_to_rg` are gone from
the local side, and with them a six-way join in every read, a
`MIN(release_group_id)` subquery in eleven queries and a
first-credited-artist subquery in nine. Measured on a real 25,966-file
library, every many-to-many that model expressed was 1:1 in the data.

- Ownership is a file. `GetFilePathsByRecordingMBIDs`,
  `LibraryMBIDIndex.CheckMBIDs`, `collectLibraryEntities` and
  `pruneStaleLocalCrossReferences` all join `audio_files`, so the 812
  orphaned recordings, 216 release groups and 260 artists that library
  carried are now structurally impossible.
- One projection: every track query selects from the `track_metadata`
  view, one row type, one mapper. Nine hand-rolled copies had drifted
  far enough to report different years on different screens.
- `library_id = 0` means every library, so each list query exists once
  instead of scoped and unscoped with a branch at every call site.
- No migration chain. `sql/schemas/` is the one description of the
  shape; `sql/migrations/`, `applyMigrations` and `schema_migrations`
  are squashed away, along with the drift between them that had sqlc
  generating against a stale schema.
- `database.InsertTestTrack` is the one test seeder; twenty test files
  had been assembling the old FK chain each in its own order.

## The catalog stores its ids as bytes

`explore_index`'s three 36-char MBID columns and its entity-type text
are 16 raw bytes and a small integer. The table and its six indexes go
780 MB to 405 MB on a real 2,052,200-row catalog, which is why a fresh
install is ~0.6 GB rather than ~1.0 GB.

- `backend/explore/mbid.go` is the only place the encoding is known;
  everything above it speaks dashed strings.
- `CHECK(length(mbid) = 16)` makes a stringly write fail at the insert
  rather than silently returning no rows, since SQLite does not coerce
  between TEXT and BLOB.
- The importer asks the artifact what encoding it carries and converts
  on the way in, so the artifact already published keeps working and no
  format bump is needed.
- `indexRowColumns`/`scanIndexRow` replace four copies of a 22-column
  list, and `TestStoredEncodingRoundTrips` sweeps every read path.

## An album page that says how much of the album is yours

- One question, asked once: is there a file. `filePaths` is filled by a
  single batched lookup when the tracklist settles, and the badge, the
  Play count, the dimmed rows and every menu item read it — replacing
  four claims of decreasing confidence that could show a green tick on
  an album whose every action did nothing.
- Play, Play 7 of 12, or no play button at all.
- `total_tracks` on `explore_index` (~2 bytes over 400,677 release
  groups) and on `audio_files` from tags that have always carried it:
  a complete MBID-matched album now makes no catalog call at all, where
  it used to spend the most expensive request the app makes.
- A merged cluster shows the running order the most releases agree on,
  and the version list marks the release you own rather than standing a
  synthetic entry in for it.
- `AlbumReleasesFailed`: a slow fetch is no longer reported as a failed
  one by a 12-second timer.
- Rows not in the library are dimmed in place (with `aria-disabled`)
  instead of the owned ones wearing a green tick and a legend.

## Caches and cover art get ceilings

- Only the three tiers of a cover are stored; the full-resolution copy
  nothing rendered was 1,134 MB of a 1.4 GB covers directory.
- One artist portrait is downloaded and the rest are remembered as
  URLs — 4.1 GB of a 5.3 GB cache was candidates no code path reads.
- `browsedArtBudget` and `httpCacheBudget` bound what an age cannot:
  the same install held art for 5,770 artists in a 1,301-artist
  library.
- `OrphanedArtistImagesJob` joined a bare MBID onto a sharded
  directory, so it deleted the rows that were the only record of the
  files it left behind. `explore.ArtistImageDir` is that layout's one
  definition now.

## The autotag queue asks whether there is work

`tagging_items` was a row per album folder, not a queue, and no query
read the `tag_status` column that held the answer. The four queue
queries ask the files, which matters most where it is least visible:
`startPrefetch` was scoring every album in a tagged library against
MusicBrainz.

## Phantom playlist tracks resolve in place

An M3U8 imported before its files leaves phantom rows; they now match
by path and fall back to position, keep their place in the playlist
when resolved, and pair best-first so two phantoms cannot claim the
same file.

## Playing a track plays the list it is in

Double-click, and Play on a single row's menu, queue the list as
displayed with `startIndex` on that row — the album page and the track
list used to queue one track and discard the album around it. A
multi-row selection still plays exactly itself.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AfVYUVExXsx1nSWrXN8mAh

backend/database/sql/sqlcgen/home.sql.go

@@ -12,10 +12,10 @@ import (
 
 const homeAlbumsByGenre = `-- name: HomeAlbumsByGenre :many
 SELECT rg.id AS album_id
-FROM release_groups rg
-JOIN release_group_recordings rgr ON rgr.release_group_id = rg.id
-JOIN recording_genres rgen ON rgen.recording_id = rgr.recording_id
-JOIN genres g ON g.id = rgen.genre_id
+FROM albums rg
+JOIN audio_files af ON af.album_id = rg.id
+JOIN file_genres fg ON fg.audio_file_id = af.id
+JOIN genres g ON g.id = fg.genre_id
 WHERE g.name = ?
 GROUP BY rg.id
 ORDER BY RANDOM()
@@ -54,9 +54,8 @@ func (q *Queries) HomeAlbumsByGenre(ctx context.Context, arg HomeAlbumsByGenrePa
 
 const homeMostPlayedAlbums = `-- name: HomeMostPlayedAlbums :many
 SELECT rg.id AS album_id
-FROM release_groups rg
-JOIN release_group_recordings rgr ON rgr.release_group_id = rg.id
-JOIN audio_files af ON af.recording_id = rgr.recording_id
+FROM albums rg
+JOIN audio_files af ON af.album_id = rg.id
 GROUP BY rg.id
 HAVING SUM(af.play_count) > 0
 ORDER BY SUM(af.play_count) DESC
@@ -89,9 +88,8 @@ func (q *Queries) HomeMostPlayedAlbums(ctx context.Context, limit int64) ([]int6
 
 const homeRandomAlbums = `-- name: HomeRandomAlbums :many
 SELECT rg.id AS album_id
-FROM release_groups rg
-JOIN release_group_recordings rgr ON rgr.release_group_id = rg.id
-JOIN audio_files af ON af.recording_id = rgr.recording_id
+FROM albums rg
+JOIN audio_files af ON af.album_id = rg.id
 GROUP BY rg.id
 ORDER BY RANDOM()
 LIMIT ?
@@ -122,9 +120,8 @@ func (q *Queries) HomeRandomAlbums(ctx context.Context, limit int64) ([]int64, e
 
 const homeRecentlyAddedAlbums = `-- name: HomeRecentlyAddedAlbums :many
 SELECT rg.id AS album_id
-FROM release_groups rg
-JOIN release_group_recordings rgr ON rgr.release_group_id = rg.id
-JOIN audio_files af ON af.recording_id = rgr.recording_id
+FROM albums rg
+JOIN audio_files af ON af.album_id = rg.id
 GROUP BY rg.id
 ORDER BY MAX(af.id) DESC
 LIMIT ?
@@ -159,9 +156,8 @@ func (q *Queries) HomeRecentlyAddedAlbums(ctx context.Context, limit int64) ([]i
 const homeRecentlyPlayedAlbums = `-- name: HomeRecentlyPlayedAlbums :many
 
 SELECT rg.id AS album_id
-FROM release_groups rg
-JOIN release_group_recordings rgr ON rgr.release_group_id = rg.id
-JOIN audio_files af ON af.recording_id = rgr.recording_id
+FROM albums rg
+JOIN audio_files af ON af.album_id = rg.id
 WHERE af.last_played IS NOT NULL
 GROUP BY rg.id
 ORDER BY MAX(af.last_played) DESC
@@ -172,7 +168,7 @@ LIMIT ?
 //
 // Every one of these returns album ids and nothing else.  The display
 // columns (cover art, artist credit, year) already have exactly one
-// correct expression of them, in GetAllAlbumsWithDetails, and a second
+// correct expression of them, in GetAlbums, and a second
 // copy per shelf would be six more places for that to drift.  The home
 // service joins the ids back to that one album list in Go.
 // Albums with the most recent play, newest first.
@@ -201,9 +197,8 @@ func (q *Queries) HomeRecentlyPlayedAlbums(ctx context.Context, limit int64) ([]
 
 const homeStaleAlbums = `-- name: HomeStaleAlbums :many
 SELECT rg.id AS album_id
-FROM release_groups rg
-JOIN release_group_recordings rgr ON rgr.release_group_id = rg.id
-JOIN audio_files af ON af.recording_id = rgr.recording_id
+FROM albums rg
+JOIN audio_files af ON af.album_id = rg.id
 WHERE af.last_played IS NOT NULL
 GROUP BY rg.id
 HAVING MAX(af.last_played) < datetime('now', ?)
@@ -242,14 +237,12 @@ func (q *Queries) HomeStaleAlbums(ctx context.Context, arg HomeStaleAlbumsParams
 
 const homeTopArtists = `-- name: HomeTopArtists :many
 SELECT
-    COALESCE(ac.text, '') AS artist_name,
+    rg.artist_credit AS artist_name,
     SUM(af.play_count) AS plays
-FROM release_groups rg
-JOIN artist_credit ac ON ac.id = rg.album_artist_credit_id
-JOIN release_group_recordings rgr ON rgr.release_group_id = rg.id
-JOIN audio_files af ON af.recording_id = rgr.recording_id
-WHERE ac.text <> ''
-GROUP BY ac.text
+FROM albums rg
+JOIN audio_files af ON af.album_id = rg.id
+WHERE rg.artist_credit <> ''
+GROUP BY rg.artist_credit
 HAVING plays > 0
 ORDER BY plays DESC
 LIMIT ?
@@ -288,10 +281,10 @@ func (q *Queries) HomeTopArtists(ctx context.Context, limit int64) ([]HomeTopArt
 const homeTopGenres = `-- name: HomeTopGenres :many
 SELECT
     g.name AS genre,
-    COUNT(DISTINCT rgr.release_group_id) AS album_count
+    COUNT(DISTINCT af.album_id) AS album_count
 FROM genres g
-JOIN recording_genres rgen ON rgen.genre_id = g.id
-JOIN release_group_recordings rgr ON rgr.recording_id = rgen.recording_id
+JOIN file_genres fg ON fg.genre_id = g.id
+JOIN audio_files af ON af.id = fg.audio_file_id
 GROUP BY g.id
 HAVING album_count >= 3
 ORDER BY album_count DESC
@@ -331,9 +324,8 @@ func (q *Queries) HomeTopGenres(ctx context.Context, limit int64) ([]HomeTopGenr
 
 const homeUnplayedAlbums = `-- name: HomeUnplayedAlbums :many
 SELECT rg.id AS album_id
-FROM release_groups rg
-JOIN release_group_recordings rgr ON rgr.release_group_id = rg.id
-JOIN audio_files af ON af.recording_id = rgr.recording_id
+FROM albums rg
+JOIN audio_files af ON af.album_id = rg.id
 GROUP BY rg.id
 HAVING SUM(af.play_count) = 0
 ORDER BY RANDOM()