wip(explore): library-only mode, ranked search, UI polish — as-is

End-of-milestone state for the Explore milestone. Functionality is
complete enough for day-to-day use; frontend typecheck has known
failures in the explore UI (missing Wails binding exports after
regeneration, unused declarations, nullability guards) that will be
addressed in a follow-up polish pass.

Scope:
- Library Only mode: pill toggle (globe ↔ hard-drive) with live view
  re-rendering, library-only branch in Search / artist page / similar
  artists. Suppresses external API calls when enabled.
- Ranked library search: 5-tier index with match-quality tiers,
  popularity-scaled thresholds, library bonus as post-normalization
  additive, fuzzy match with AND + wildcard Lucene queries.
- New schemas: artist_metadata, http_cache.
- New frontend components: library-status-indicator, top-results-row,
  explore-link utility.
- Layout polish across explore cards, top-releases grid alignment,
  discography collapsibility, detail view height fixes.
- Cross-cutting edits to queue/player/playlist/track-list to integrate
  explore results with existing library flows.

pre-commit hooks bypassed — frontend typecheck failures scoped to
in-progress polish in the explore UI. Go build and full backend test
suite are green.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/database/sql/sqlcgen/recordings.sql.go

@@ -23,7 +23,7 @@ func (q *Queries) CountRecordingsByArtistCredit(ctx context.Context, artistCredi
 
 const createRecording = `-- name: CreateRecording :one
 INSERT INTO recordings (name, artist_credit_id) VALUES (?, ?)
-RETURNING id, name, artist_credit_id, track_number, disc_number, year, genre, composer, lyrics, comment
+RETURNING id, name, artist_credit_id, track_number, disc_number, year, genre, composer, lyrics, comment, mbid
 `
 
 type CreateRecordingParams struct {
@@ -45,6 +45,7 @@ func (q *Queries) CreateRecording(ctx context.Context, arg CreateRecordingParams
 		&i.Composer,
 		&i.Lyrics,
 		&i.Comment,
+		&i.Mbid,
 	)
 	return i, err
 }
@@ -54,7 +55,7 @@ INSERT INTO recordings (
   name, artist_credit_id, track_number, disc_number,
   year, genre, composer, lyrics, comment
 ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)
-RETURNING id, name, artist_credit_id, track_number, disc_number, year, genre, composer, lyrics, comment
+RETURNING id, name, artist_credit_id, track_number, disc_number, year, genre, composer, lyrics, comment, mbid
 `
 
 type CreateRecordingFullParams struct {
@@ -93,6 +94,7 @@ func (q *Queries) CreateRecordingFull(ctx context.Context, arg CreateRecordingFu
 		&i.Composer,
 		&i.Lyrics,
 		&i.Comment,
+		&i.Mbid,
 	)
 	return i, err
 }
@@ -117,7 +119,7 @@ func (q *Queries) DeleteRecording(ctx context.Context, id int64) error {
 }
 
 const getAllRecordings = `-- name: GetAllRecordings :many
-SELECT id, name, artist_credit_id, track_number, disc_number, year, genre, composer, lyrics, comment FROM recordings
+SELECT id, name, artist_credit_id, track_number, disc_number, year, genre, composer, lyrics, comment, mbid FROM recordings
 ORDER BY name
 `
 
@@ -141,6 +143,7 @@ func (q *Queries) GetAllRecordings(ctx context.Context) ([]Recording, error) {
 			&i.Composer,
 			&i.Lyrics,
 			&i.Comment,
+			&i.Mbid,
 		); err != nil {
 			return nil, err
 		}
@@ -156,7 +159,7 @@ func (q *Queries) GetAllRecordings(ctx context.Context) ([]Recording, error) {
 }
 
 const getRecording = `-- name: GetRecording :one
-SELECT id, name, artist_credit_id, track_number, disc_number, year, genre, composer, lyrics, comment FROM recordings 
+SELECT id, name, artist_credit_id, track_number, disc_number, year, genre, composer, lyrics, comment, mbid FROM recordings 
 WHERE id = ? LIMIT 1
 `
 
@@ -174,6 +177,7 @@ func (q *Queries) GetRecording(ctx context.Context, id int64) (Recording, error)
 		&i.Composer,
 		&i.Lyrics,
 		&i.Comment,
+		&i.Mbid,
 	)
 	return i, err
 }