Implement file hash-based library matching and remove fuzzy ASIN matching

Adds file hash-based matching for Audiobookshelf library items to ensure 100% accurate ASIN assignment for RMAB-organized content. Removes fuzzy matching from library availability checks, making all matching ASIN-only to eliminate false positives and race conditions. Updates database schema, processors, and matcher utilities; adds new tests and documentation for the new matching strategy. Removes obsolete scripts, Dockerfile, and related tests; updates docker-compose for test environments.

documentation/admin-features/request-deletion.md

@@ -96,7 +96,11 @@ model Request {
    - **Audiobookshelf Mode:** Delete library item via API if `absItemId` exists
      - Prevents "ghost" entries in Audiobookshelf library
      - Only removes from ABS database, not files (already deleted in step 3)
-   - **Plex Mode:** Clear plex_library cache records
+   - **Plex Mode:** Delete library item via API if `plexGuid` exists
+     - Queries plex_library table to get plexRatingKey from audiobook's plexGuid
+     - Calls Plex DELETE `/library/metadata/{ratingKey}` endpoint with the ratingKey
+     - Requires deletion enabled in Plex: Settings > Server > Library
+     - Also clears plex_library cache records
 
 5. **Soft Delete Request**
    - UPDATE: `deletedAt = NOW(), deletedBy = adminUserId`
@@ -194,6 +198,9 @@ where: {
 8. ✅ **Network error** - Alert shown, request remains
 9. ✅ **ABS library item deletion fails** - Log error, continue with soft delete
 10. ✅ **No absItemId present** - Skip ABS deletion (not yet in library)
+11. ✅ **Plex library item deletion fails** - Log error, continue with soft delete
+12. ✅ **No plexGuid present** - Skip Plex deletion (not yet in library)
+13. ✅ **Plex deletion not enabled in settings** - Log error, continue with soft delete
 
 ## File Structure