feat(async): Add django-q2 with ORM broker and demo job

[taylor-osler-sentry]

Summary

• Adds django-q2 as a dependency and configures it with the ORM broker (backed by the existing PostgreSQL default database)
• Introduces firetower.incidents.tasks.schedule_demo as the first queue task (stub that prints "hello world"), registered via a data migration
• Extends docker/entrypoint.sh with a worker command that starts qcluster, and refactors all branches to use exec for proper signal handling in Docker

Test plan

• Run python manage.py migrate — confirm 0015_schedule_demo applies cleanly and a schedule_slo_nag row appears in django_q_schedule
• Run python manage.py qcluster — confirm the worker starts and picks up the scheduled task
• Run docker/entrypoint.sh worker — confirm the container starts the qcluster process
• Unapply migration (migrate incidents 0014) — confirm the schedule row is removed

🤖 Generated with Claude Code

[linear-code]

RELENG-538 Stand up some kind of async task running capability for Firetower

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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[cursor]

Migration imports mutable runtime code from tasks module

Medium Severity

The migration imports SCHEDULES from firetower.incidents.tasks at module level, coupling it to mutable runtime code. If SCHEDULES is ever renamed, restructured, or the "schedule_demo" key is removed, this migration will break on any fresh database. Additionally, importing tasks.py triggers from firetower.incidents.models import Incident, pulling in the live model class rather than the historical version — and any future import-time side effects in tasks.py will also fire during migration. The schedule data (func, schedule_type, minutes, repeats) can be inlined directly in the migration to keep it self-contained.

Additional Locations (1)

• src/firetower/incidents/migrations/0015_schedule_demo.py#L9-L10

 

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