Usage tracking failed silently when FTP download failed (fallback archive
with no 3MF), when printing from external spool holder (VT tray not
iterated by AMS fallback), and notifications showed "Unknown" for time
and filament. Now resolves 3MF from library/previous archives, tracks
VT tray remain% deltas, enriches notifications with usage tracker
results, and captures print time from MQTT for fallback archives.