Schedule Batch Events registry rows from Airflow

[krowvin]

Parent: USACE/cwms-data-api#1772

Summary

• Adds registry-driven Airflow scheduling through Batch Events instead of direct AWS Batch submission.
• Supports default or per-office scheduler Keycloak clients and optional configured scheduled office lists.
• Evaluates hourly and cron schedules in each script's scheduleTimezone; DST gaps are skipped and repeated occurrences run once.

Validation

• python -m pytest tests\dags\unit\test_batch_events_helper.py -q
• Docker Airflow DAG harness was run during the broader end-to-end verification.