fix: reduce log noise during catalogue/book scrapes

Demote per-book and per-chapter-list-page Info logs to Debug — these
fire hundreds of times per catalogue run and drown out meaningful signals:
- orchestrator: RunBook starting (per book)
- metadata saved (per book)
- chapter list fetched (per book)
- scraping chapter list page N (per pagination page per book)

The 'book scrape finished' summary log (with scraped/skipped/errors
counters) remains at Info — it is the useful signal per book.

backend/internal/novelfire/scraper.go

@@ -241,7 +241,7 @@ func (s *Scraper) ScrapeChapterList(ctx context.Context, bookURL string, upTo in
 		}
 
 		pageURL := fmt.Sprintf("%s?page=%d", baseChapterURL, page)
-		s.log.Info("scraping chapter list", "page", page, "url", pageURL)
+		s.log.Debug("scraping chapter list", "page", page, "url", pageURL)
 
 		raw, err := retryGet(ctx, s.log, s.client, pageURL, 9, 6*time.Second)
 		if err != nil {

backend/internal/orchestrator/orchestrator.go

@@ -68,7 +68,7 @@ func New(cfg Config, novel scraper.NovelScraper, store bookstore.BookWriter, log
 // Returns a ScrapeResult with counters. The result's ErrorMessage is non-empty
 // if the run failed at the metadata or chapter-list level.
 func (o *Orchestrator) RunBook(ctx context.Context, task domain.ScrapeTask) domain.ScrapeResult {
-	o.log.Info("orchestrator: RunBook starting",
+	o.log.Debug("orchestrator: RunBook starting",
 		"task_id", task.ID,
 		"kind", task.Kind,
 		"url", task.TargetURL,
@@ -103,7 +103,7 @@ func (o *Orchestrator) RunBook(ctx context.Context, task domain.ScrapeTask) doma
 		}
 	}
 
-	o.log.Info("metadata saved", "slug", meta.Slug, "title", meta.Title)
+	o.log.Debug("metadata saved", "slug", meta.Slug, "title", meta.Title)
 
 	// ── Step 2: Chapter list ──────────────────────────────────────────────────
 	refs, err := o.novel.ScrapeChapterList(ctx, task.TargetURL, task.ToChapter)
@@ -114,7 +114,7 @@ func (o *Orchestrator) RunBook(ctx context.Context, task domain.ScrapeTask) doma
 		return result
 	}
 
-	o.log.Info("chapter list fetched", "slug", meta.Slug, "chapters", len(refs))
+	o.log.Debug("chapter list fetched", "slug", meta.Slug, "chapters", len(refs))
 
 	// Persist chapter refs (without text) so the index exists early.
 	if wErr := o.store.WriteChapterRefs(ctx, meta.Slug, refs); wErr != nil {