Update monitoring to handle multiple simultaneous torrent copy operations
using the new directory-based marker structure.
Changes:
- Rename get_active_torrent_copy() to get_active_torrent_copies()
- Read all marker files from /tmp/torrent-copy/ directory
- Return Vec<String> instead of Option<String> for multiple copies
- Display each active copy as separate sub-service
- Unsanitize filenames by replacing _ with /
This enables monitoring when multiple torrents finish simultaneously
and are being copied in parallel to permanent storage.
Christoffer Martinsson
4a8cfbbde4