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/diff.go

@@ -15,16 +15,56 @@ type MissingRelease struct {
 	ReleaseDate string `json:"release_date"`
 }
 
+// TypeFilter carries the per-artist type toggles that suppress whole release
+// categories from the missing set. It mirrors the ignore_singles /
+// ignore_compilations columns on artist_settings.
+//
+// These toggles are applied at scan/read time (not only when the MusicBrainz
+// discography is synced) so a user flipping a toggle takes effect immediately on
+// the dashboard, artist page, and Telegram digest — rather than waiting for the
+// artist's MusicBrainz cache to expire and the rows to be pruned on the next
+// cache-miss re-sync.
+type TypeFilter struct {
+	IgnoreSingles      bool
+	IgnoreCompilations bool
+}
+
+// suppressed reports whether an external release is dropped by the type toggles.
+// A release counts as a Single/Compilation via either its primary Type or its
+// secondary types, matching musicbrainz.FilterReleaseGroups so both the
+// cache-miss (store-time) and read-time paths agree.
+func (f TypeFilter) suppressed(ext database.ExternalRelease) bool {
+	if f.IgnoreSingles && (ext.Type == "Single" || hasType(ext.SecondaryTypes, "Single")) {
+		return true
+	}
+	if f.IgnoreCompilations && (ext.Type == "Compilation" || hasType(ext.SecondaryTypes, "Compilation")) {
+		return true
+	}
+	return false
+}
+
+// hasType reports whether types contains want.
+func hasType(types []string, want string) bool {
+	for _, t := range types {
+		if t == want {
+			return true
+		}
+	}
+	return false
+}
+
 // FindMissingReleases compares an artist's external discography against the
 // user's local albums and returns the releases that are present externally but
 // have no sufficiently similar local album.
 //
 // Rules:
 //   - External releases flagged IsIgnored are never reported.
+//   - External releases suppressed by the per-artist type toggles (filter) are
+//     never reported.
 //   - A local album only matches an external release for the same ArtistID.
 //   - An external release is "missing" when none of the local albums (same
 //     ArtistID) IsMatch at the given threshold.
-func FindMissingReleases(local []database.LocalAlbum, external []database.ExternalRelease, threshold float64) []MissingRelease {
+func FindMissingReleases(local []database.LocalAlbum, external []database.ExternalRelease, threshold float64, filter TypeFilter) []MissingRelease {
 	// Resolve the threshold exactly as ScanArtist/ScanAll do, so the exported
 	// primitive honors the same zero-means-default contract rather than treating
 	// 0 as "always match" (which would report nothing as missing).
@@ -41,6 +81,9 @@ func FindMissingReleases(local []database.LocalAlbum, external []database.Extern
 		if ext.IsIgnored {
 			continue
 		}
+		if filter.suppressed(ext) {
+			continue
+		}
 
 		albums := localByArtist[ext.ArtistID]
 		matched := false