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/phase3/ranking-algorithm.md

@@ -26,13 +26,16 @@ Evaluates and scores torrents to automatically select best audiobook download.
 
 **Stage 2: Title Matching (0-35 pts)**
 - Only scored if Stage 1 passes
+- **Tries full title first, then required title (without parentheses)** if no match
+  - Example: "We Are Legion (We Are Bob)" tries both full title and "We Are Legion"
+  - Handles torrents that include subtitle AND those that omit it
 - Complete title match requirements (both must be true):
   - No significant words BEFORE matched title (prevents "This Inevitable Ruin Dungeon Crawler Carl, Book 7")
   - Followed by metadata markers: " by", " [", " -", " (", " {", " :", ","
 - Complete match → 35 pts
 - Title has prefix/suffix words OR continues with more words → fuzzy similarity (partial credit)
 - Prevents series confusion: "The Housemaid" vs "The Housemaid's Secret", "Dungeon Crawler Carl" vs "Book 7"
-- No substring match → fuzzy similarity (partial credit)
+- No substring match → fuzzy similarity (best score from full or required title)
 
 **Stage 3: Author Matching (0-15 pts)**
 - Exact substring match → proportional credit