Three bugs fixed and one recovery feature added:
1. AMS remain=0 zeroed all spools on printer power-off. The weight sync
treated 0% remain as "fully consumed," setting weight_used to
label_weight for every assigned spool. Fix: skip remain=0 in AMS
weight sync — empty spools are tracked by the usage tracker.
2. Editing any spool field sent stale weight_used from the React Query
cache back to the server, resetting usage-tracked weight. Fix: only
include weight_used in PATCH when the user explicitly changes it.
3. K-profile auto-select crashed on dual-nozzle printers for non-BL
spools with 'SpoolKProfile has no attribute extruder_id'. The model
attribute is 'extruder', not 'extruder_id'.
4. New "Sync Weights from AMS" button in Settings > Filament Tracking
(built-in inventory mode) to force-recover spool weights from live
AMS sensor data. Bypasses the "only increase" guard for explicit
user-initiated recovery.
