fix: address fourth code review findings

- Fix FK constraint violation in SyncArtistDiscography: delete
  notifications_sent rows before external_releases to prevent
  constraint failure when re-syncing artists with prior notifications.
- Implement per-artist type filtering: FilterReleaseGroups now accepts
  FilterOptions with IgnoreSingles/IgnoreCompilations flags, read from
  artist_settings table via getArtistFilterOptions.
- Fix inconsistent error wrapping: GetExternalRelease now wraps errors
  with fmt.Errorf like all other functions in the package; updated test
  to use errors.Is for sql.ErrNoRows check.
- Add tests: FilterReleaseGroups ignore singles/compilations,
  SyncArtistDiscography per-artist type filtering, and FK-safe resync.

internal/musicbrainz/api_test.go

@@ -20,7 +20,7 @@ func TestFilterReleaseGroups_ExcludesBootlegPromotionPseudo(t *testing.T) {
 		{ID: "rg-4", Title: "Pseudo Release", Type: "Album", Status: "Pseudo-Release"},
 	}
 
-	result := FilterReleaseGroups(groups)
+	result := FilterReleaseGroups(groups, FilterOptions{})
 
 	if len(result) != 1 {
 		t.Fatalf("FilterReleaseGroups() returned %d groups, want 1", len(result))
@@ -41,7 +41,7 @@ func TestFilterReleaseGroups_IncludesOnlyAllowedTypes(t *testing.T) {
 		{ID: "rg-7", Title: "Remix", Type: "Remix", Status: "Official"},
 	}
 
-	result := FilterReleaseGroups(groups)
+	result := FilterReleaseGroups(groups, FilterOptions{})
 
 	if len(result) != 4 {
 		t.Fatalf("FilterReleaseGroups() returned %d groups, want 4", len(result))
@@ -55,6 +55,44 @@ func TestFilterReleaseGroups_IncludesOnlyAllowedTypes(t *testing.T) {
 	}
 }
 
+func TestFilterReleaseGroups_IgnoreSingles(t *testing.T) {
+	groups := []ReleaseGroup{
+		{ID: "rg-1", Title: "Album", Type: "Album", Status: "Official"},
+		{ID: "rg-2", Title: "Single", Type: "Single", Status: "Official"},
+		{ID: "rg-3", Title: "EP", Type: "EP", Status: "Official"},
+	}
+
+	result := FilterReleaseGroups(groups, FilterOptions{IgnoreSingles: true})
+
+	if len(result) != 2 {
+		t.Fatalf("FilterReleaseGroups() returned %d groups, want 2", len(result))
+	}
+	for _, rg := range result {
+		if rg.Type == "Single" {
+			t.Errorf("single %q should have been filtered out", rg.ID)
+		}
+	}
+}
+
+func TestFilterReleaseGroups_IgnoreCompilations(t *testing.T) {
+	groups := []ReleaseGroup{
+		{ID: "rg-1", Title: "Album", Type: "Album", Status: "Official"},
+		{ID: "rg-2", Title: "Compilation", Type: "Compilation", Status: "Official"},
+		{ID: "rg-3", Title: "EP", Type: "EP", Status: "Official"},
+	}
+
+	result := FilterReleaseGroups(groups, FilterOptions{IgnoreCompilations: true})
+
+	if len(result) != 2 {
+		t.Fatalf("FilterReleaseGroups() returned %d groups, want 2", len(result))
+	}
+	for _, rg := range result {
+		if rg.Type == "Compilation" {
+			t.Errorf("compilation %q should have been filtered out", rg.ID)
+		}
+	}
+}
+
 // ---------- NormalizeString tests ----------
 
 func TestNormalizeString_Basic(t *testing.T) {