fix: address code review findings

- Honor ignore_singles/ignore_compilations at scanner read time so toggles
  take effect immediately on the dashboard, artist page, and digest instead
  of waiting for the MusicBrainz cache to expire and prune rows.
- Run notifier notify synchronously in the scheduler loop to avoid overlapping
  read-send-mark runs double-sending the digest.
- Show artist name (with ID fallback) on the archive page instead of raw IDs.
- Select last_synced in GetAllArtistSettings for contract consistency.
- Fix stale startPeriodicSync comment and remove redundant error var.
- Remove dead ignored-branch from the artist template (never rendered).
- Add tests: CSRF sameOrigin, ArtistCacheFresh, secondary_types round-trip,
  and scanner type-toggle filtering.
- Update Specification.md schema/config to reflect mbid, last_synced,
  secondary_types, sync.interval, and server.public_url.

internal/scanner/scan.go

@@ -28,7 +28,19 @@ func ScanArtist(ctx context.Context, db *database.DB, artistID string, threshold
 		return nil, err
 	}
 
-	missing := FindMissingReleases(local, external, threshold)
+	// Apply the artist's type toggles at read time so ignore_singles /
+	// ignore_compilations changes take effect immediately, without waiting for
+	// the MusicBrainz cache to expire and prune rows on the next re-sync.
+	settings, err := database.GetArtistSettings(db, artistID)
+	if err != nil {
+		return nil, err
+	}
+	filter := TypeFilter{
+		IgnoreSingles:      settings.IgnoreSingles,
+		IgnoreCompilations: settings.IgnoreCompilations,
+	}
+
+	missing := FindMissingReleases(local, external, threshold, filter)
 	return missing, nil
 }