## Summary
Adds the minimal foundation for Cloud marketing conversion tracking:
- locked internal installation config for conversion tracking
credentials and event mappings
- generic background job and service for uploading conversion events
from stored attribution
- focused coverage for Cloud gating, click-id selection, payload shape,
and optional conversion value
This PR intentionally does not wire signup or plan activation yet. The
next step is to validate the service from Rails console against existing
attributed accounts, then add the event hooks in a follow-up PR.
## Notes
The config remains locked and is surfaced under the Internal settings
group next to the existing Cloud plan configuration. The service assumes
the locked config is present and valid; config mistakes should surface
instead of being silently ignored.
