feat(elt): Allow ELT task log level to be configured externally (#170)

### Summary

Lower default log level for ELT tasks to INFO and allow it to be
overridden.

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## Summary by CodeRabbit

* **Chores**
* Updated default log level from DEBUG to INFO. Log verbosity is now
configurable via environment variable for operational flexibility.

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Author: martyngigg

infra/ansible-docker/playbooks/elt/templates/cron/elt_task.sh.j2

@@ -6,7 +6,7 @@ ELT_SECRETS=${ELT_SECRETS:?}
 ELT_GIT_REF=${ELT_GIT_REF:-main}
 ELT_WRITE_DISPOSITION=${ELT_WRITE_DISPOSITION:-}
 EXTRACT_AND_LOAD_SCRIPT=extract_and_load.py
-LOG_LEVEL=DEBUG
+LOG_LEVEL=${ELT_LOG_LEVEL:-INFO}
 ON_PIPELINE_FAILURE=log_and_continue
 DBT_REQUIREMENTS_TXT=requirements.txt