Add limit_5h and limit_weekly options as alternatives to reserve_5h
and reserve_weekly for capping credential utilization. The two are
mutually exclusive per window.
Fix computeAggregatedUtilization to scale per-credential utilization
relative to each credential's cap before averaging, so external users
see correct available capacity regardless of per-credential caps.
Fix pickLeastUsed to compare remaining capacity (cap - utilization)
instead of raw utilization, ensuring fair comparison across credentials
with different caps.
566abb00cd