Add multi-source ebook search & processing

Refactor ebook flow to support multiple sources (Anna's Archive direct downloads + Prowlarr indexer search) and unify handling with existing audiobook processors. Key changes:
- search-ebook.processor: rewritten to try Anna's Archive first then fall back to indexer search, add Prowlarr grouping, ranking (rankEbookTorrents), and handlers to route results to direct-download or download-torrent flows.
- organize-files.processor: enriches audiobook/ebook metadata from AudibleCache (year, narrator), treats indexer downloads specially (seed retention), adds optional NZB cleanup/archive logic, and improves retryable error detection.
- file-organizer: organizeEbook now accepts additional metadata and an isIndexerDownload flag and supports directories vs single-file paths.
- API/UI: include request.type in admin requests API and remove the “coming soon” notice from Ebook settings tab.
- fetch-ebook route: removed blocking error for indexer-only mode so the flow can proceed when indexer search is enabled.
- Documentation: update TOC, ebook-sidecar, settings-pages, and ranking-algorithm docs to describe indexer search, unified ebook ranking, configuration, and flows.
These changes enable indexer-based ebook discovery, ranking, and downloads while preserving existing Anna's Archive behavior and reusing audiobook download processors where possible.

documentation/TABLEOFCONTENTS.md

@@ -41,10 +41,11 @@
 ## E-book Support (First-Class)
 - **First-class ebook requests, separate tracking** → [integrations/ebook-sidecar.md](integrations/ebook-sidecar.md)
 - **Multi-source ebook downloads (Anna's Archive + Indexer Search)** → [integrations/ebook-sidecar.md](integrations/ebook-sidecar.md)
+- **Ebook indexer search (Prowlarr with ebook categories)** → [integrations/ebook-sidecar.md](integrations/ebook-sidecar.md#flow-indexer-search)
 - **ASIN-based matching, format selection** → [integrations/ebook-sidecar.md](integrations/ebook-sidecar.md)
-- **Ebook ranking algorithm (inverted size scoring)** → [integrations/ebook-sidecar.md](integrations/ebook-sidecar.md)
+- **Ebook ranking algorithm (unified with audiobooks)** → [phase3/ranking-algorithm.md](phase3/ranking-algorithm.md#ebook-torrent-ranking)
 - **Direct HTTP downloads from Anna's Archive** → [integrations/ebook-sidecar.md](integrations/ebook-sidecar.md)
-- **Ebook delete behavior (files only)** → [integrations/ebook-sidecar.md](integrations/ebook-sidecar.md)
+- **Ebook delete behavior (files only, torrents seed)** → [integrations/ebook-sidecar.md](integrations/ebook-sidecar.md#delete-behavior)
 - **Ebook settings (3-section UI)** → [settings-pages.md](settings-pages.md#e-book-sidecar)
 - **Indexer categories (audiobook/ebook tabs)** → [settings-pages.md](settings-pages.md#indexer-categories-tabbed)
 
@@ -116,7 +117,9 @@
 **"How does e-book support work?"** → [integrations/ebook-sidecar.md](integrations/ebook-sidecar.md)
 **"How do I enable e-book downloads?"** → [integrations/ebook-sidecar.md](integrations/ebook-sidecar.md), [settings-pages.md](settings-pages.md#e-book-sidecar)
 **"How do I configure ebook sources (Anna's Archive vs Indexer)?"** → [settings-pages.md](settings-pages.md#e-book-sidecar)
+**"How does ebook indexer search work?"** → [integrations/ebook-sidecar.md](integrations/ebook-sidecar.md#flow-indexer-search)
 **"How do I configure ebook categories per indexer?"** → [settings-pages.md](settings-pages.md#indexer-categories-tabbed)
+**"How does ebook ranking work?"** → [phase3/ranking-algorithm.md](phase3/ranking-algorithm.md#ebook-torrent-ranking)
 **"What happens when I delete an ebook request?"** → [integrations/ebook-sidecar.md](integrations/ebook-sidecar.md#delete-behavior)
 **"Why do ebook requests have an orange badge?"** → [integrations/ebook-sidecar.md](integrations/ebook-sidecar.md#ui-representation)
 **"How do scheduled jobs work?"** → [backend/services/scheduler.md](backend/services/scheduler.md)