improve lastfm playlist parity and fallback resolution

Queue resolved last.fm tracks as playlist media to preserve playlist semantics, and add a robust mirror-based parser fallback for last.fm temporary unavailable responses while keeping track order and duplicates.

internal/app/app.go

@@ -178,6 +178,47 @@ func (m *Main) AddByID(ctx context.Context, source, mediaType, id string) error
 	return nil
 }
 
+func (m *Main) AddPlaylistByTrackIDs(ctx context.Context, source, playlistID, playlistName string, trackIDs []string) error {
+	p, err := m.GetLoggedInProvider(ctx, source)
+	if err != nil {
+		return err
+	}
+	if strings.TrimSpace(playlistName) == "" {
+		playlistName = playlistID
+	}
+	ids := make([]string, 0, len(trackIDs))
+	for _, id := range trackIDs {
+		id = strings.TrimSpace(id)
+		if id != "" {
+			ids = append(ids, id)
+		}
+	}
+	if len(ids) == 0 {
+		return fmt.Errorf("playlist %q has no track ids", playlistName)
+	}
+
+	pending := media.PendingFunc{
+		ResolveFn: func(context.Context) (media.Media, error) {
+			metaItems := make([]any, 0, len(ids))
+			for _, id := range ids {
+				metaItems = append(metaItems, map[string]any{"id": id})
+			}
+			playlistMeta := map[string]any{
+				"name":   playlistName,
+				"tracks": map[string]any{"items": metaItems},
+			}
+			return media.MediaFunc{RipFn: func(ctx context.Context) error {
+				if m.Config.Session.CLI.TextOutput {
+					m.logf("Downloading playlist: %s\n", playlistName)
+				}
+				return m.ripPlaylist(ctx, p, source, playlistID, playlistMeta)
+			}}, nil
+		},
+	}
+	m.Pending = append(m.Pending, pending)
+	return nil
+}
+
 func (m *Main) ripCollection(ctx context.Context, p provider.Client, source, kind, id string, meta map[string]any) error {
 	name := titleFromMetadata(meta, id)
 	if n := stringFromAny(meta["name"]); n != "" {