Audible: HTML refresh, multi-narrator & works dedup

Switch nightly discovery refresh to scrape Audible's curated HTML storefronts (popular, new releases, category pages) while keeping real-time user paths on the JSON catalog API. Add robust HTML resilience knobs (increased retries, capped jittered backoff, AdaptivePacer changes and per-batch cooldowns) to avoid failing nightly jobs during 503 storms. Implement multi-narrator capture via a new extractAllNarrators helper and update parsers to preserve all narrator anchors. Introduce two-pass dedup: in-memory deduplicateAndCollectGroups + collapseByExistingWorks that consults the works table, export metadataScore for consistent representative selection, and persist dedup groups (fire-and-forget). Wire collapseByExistingWorks into search/author/series routes and make defensive dedup in the refresh processor. Add HTML parsing helpers, runtime/lang-aware parsing, jitteredBackoff cap, and tests for the new behaviors.

documentation/TABLEOFCONTENTS.md

@@ -45,6 +45,8 @@
 - **Web scraping (popular, new releases)** → [integrations/audible.md](integrations/audible.md)
 - **Database caching, real-time matching** → [integrations/audible.md](integrations/audible.md)
 - **Book covers API for login page** → [frontend/pages/login.md](frontend/pages/login.md)
+- **Dedup & works table (cross-ASIN identity)** → [integrations/audible.md](integrations/audible.md#dedup--works-table)
+- **Multi-narrator capture in HTML scrapers** → [integrations/audible.md](integrations/audible.md#narrator-capture-in-html-scrapers)
 
 ## E-book Support (First-Class)
 - **First-class ebook requests, separate tracking** → [integrations/ebook-sidecar.md](integrations/ebook-sidecar.md)