lastSeen tracked workspacesQ.dataUpdatedAt which updates on every background
refetch, creating a new metrics object reference each cycle. The useEffect
dep on metrics then fired unconditionally, calling onMetrics → setMetricsById
→ Dashboard re-render → another refetch → infinite loop.
computeFleetAggregates never reads lastSeen, so reporting it upward was
pointless. Hardcode null and drop it from the dep array entirely.
f79cdafba7