API endpoint for checking account balance and remaining CU

Users want to automatically monitor their account balance and CU usage to set up alerts in Prometheus/Blackbox Exporter, Grafana, and other monitoring systems.
GetBlock currently does not provide a public API that returns:

• current account balance (USD or CU),

• CU included in the plan,

• CU usage and remaining CU,

• estimated time until depletion.