Fix file copy location to respect configured media directory

Previously, files were always being copied to /media/audiobooks regardless
of the configured media directory in settings. This was caused by:

1. FileOrganizer singleton reading from MEDIA_DIR env var (never set)
   instead of database config 'media_dir'
2. Hardcoded /media/audiobooks fallback being used when env var not found
3. Three locations passing hardcoded paths to addOrganizeJob (unused)

Changes:
- Modified getFileOrganizer() to read media_dir from database config
- Made targetPath parameter optional in addOrganizeJob (not used by processor)
- Removed hardcoded /media/audiobooks paths from all addOrganizeJob calls
- Updated organize-files processor to await getFileOrganizer()
- Updated documentation to reflect configuration behavior

Files now correctly copy to the directory configured in setup wizard or
settings page, with /media/audiobooks only as fallback if not configured.

Fixes: User-reported issue where configured media directory was ignored

src/lib/processors/monitor-download.processor.ts

@@ -117,13 +117,12 @@ export async function processMonitorDownload(payload: MonitorDownloadPayload): P
         throw new Error('Request or audiobook not found');
       }
 
-      // Trigger organize files job
+      // Trigger organize files job (target path determined by database config)
       const jobQueue = getJobQueueService();
       await jobQueue.addOrganizeJob(
         requestId,
         request.audiobook.id,
-        `${downloadPath}/${torrent.name}`,
-        `/media/audiobooks/${request.audiobook.author}/${request.audiobook.title}`
+        `${downloadPath}/${torrent.name}`
       );
 
       await logger?.info(`Triggered organize_files job for request ${requestId}`);