refactor(podcasts): drop the dead downloadRoot param on upsertEpisode

FilePath is library-relative (the pinned layout resolves at download
time via the library folders); the parameter never carried a value.

internal/services/podcast_service.go

@@ -387,7 +387,7 @@ func (s *PodcastService) applyFetch(ctx context.Context, feed *database.PodcastF
 
 	count := 0
 	for i := range parsed.Channel.Items {
-		if err := s.upsertEpisode(ctx, feed, root, feedSlug, &parsed.Channel.Items[i], i+1); err != nil {
+		if err := s.upsertEpisode(ctx, feed, feedSlug, &parsed.Channel.Items[i], i+1); err != nil {
 			// One bad item must not sink the batch.
 			log.Printf("[PODCAST] episode upsert failed for feed %s item %d: %v", feed.ID, i+1, err)
 			continue
@@ -418,8 +418,9 @@ func (s *PodcastService) applyFetch(ctx context.Context, feed *database.PodcastF
 // upsertEpisode maps one XML item onto a media_items row (plan §5 field
 // inventory). Positions are 1-based, renumbered per fetch; file_path is
 // the PLANNED final layout — the upsert only applies it to rows that
-// are not yet downloaded (query-side guard).
+// are not yet downloaded (query-side guard); the abs root resolves at
-func (s *PodcastService) upsertEpisode(ctx context.Context, feed *database.PodcastFeeds, downloadRoot, feedSlug string, item *PodcastItemXML, position int) error {
+// download time via the library folders.
+func (s *PodcastService) upsertEpisode(ctx context.Context, feed *database.PodcastFeeds, feedSlug string, item *PodcastItemXML, position int) error {
 	title := item.EpisodeTitle()
 	if title == "" {
 		title = fmt.Sprintf("Episode %d", position)
@@ -477,7 +478,6 @@ func (s *PodcastService) upsertEpisode(ctx context.Context, feed *database.Podca
 		Hosts:         truncateSlice(hosts, 255),
 		Guests:        truncateSlice(guests, 255),
 	})
-	_ = downloadRoot // layout is relative; abs root resolves at download time
 	return err
 }