* feat(check_batch_cost.py): emit spend log on successful request
ensures cost tracked for batch requests
* feat(proxy_server.py): add background job to poll completed batch jobs
used for calculating cost for batch jobs
* fix(proxy_server.py): run batch cost tracking job every hour
batch jobs take time to complete, no need to run every few seconds
* feat(proxy_server.py): run batch cost tracking job every hour
