Add SABnzbd Usenet/NZB integration and documentation

Introduces SABnzbd as a supported download client for Usenet/NZB alongside qBittorrent, including service implementation, setup wizard and admin settings UI updates, and protocol-specific job processor logic. Updates documentation, PRD, and database schema to support NZB downloads, adds comprehensive technical details and testing strategies, and fixes Audible integration issues related to search and ASIN extraction.

documentation/integrations/audible.md

@@ -144,3 +144,25 @@ interface EnrichedAudibleAudiobook extends AudibleAudiobook {
 - Redis (caching, optional)
 - Database (PostgreSQL)
 - string-similarity (matching)
+
+## Fixed Issues
+
+**Search returning empty results (2026-01-07)**
+- **Problem:** Audible changed HTML structure for search results from `.productListItem` to `.s-result-item`
+- **Impact:** All search queries returned 0 results
+- **Fix:** Updated `search()` method to support both `.s-result-item` (current) and `.productListItem` (legacy)
+- **Selectors updated:**
+  - Main: `.s-result-item, .productListItem`
+  - Title: `h2` (new) or `h3 a` (legacy)
+  - Author: `a[href*="/author/"]` (new) or `.authorLabel` (legacy)
+  - Narrator: `a[href*="searchNarrator="]` (new) or `.narratorLabel` (legacy)
+  - Runtime: `span:contains("Length:")` (new) or `.runtimeLabel` (legacy)
+  - Rating: `.a-icon-star span` (new) or `.ratingsLabel` (legacy)
+- **Location:** `src/lib/integrations/audible.service.ts:235`
+
+**Some audiobooks missing from search results (2026-01-07)**
+- **Problem:** ASIN extraction only matched `/pd/` URLs but some audiobooks use `/ac/` URLs
+- **Impact:** Books like "Beatitude" by DJ Krimmer (ASIN: B0DVH7XL36) were skipped
+- **Fix:** Updated ASIN regex to match both `/pd/` and `/ac/` URL patterns: `/\/(?:pd|ac)\/[^\/]+\/([A-Z0-9]{10})/`
+- **Location:** `src/lib/integrations/audible.service.ts:75, 161, 240`
+- **Affects:** `getPopularAudiobooks()`, `getNewReleases()`, `search()` methods