Grafana dashboards live in git rather than only in the instance

## Summary

Evaluate Grafana Git Sync for mirroring dashboards to a repository, so dashboard definitions are versioned and reviewable instead of edited in place and lost on rebuild.

## Motivation

Dashboards are accumulating. #249 adds them for the stateless tier, #228 broadens GCP coverage, #152 adds Scrutiny SMART metrics — and each one exists only inside the Grafana instance. A hand-edit there is unreviewable, unattributable, and gone if the instance is rebuilt.

That contradicts how everything else here is managed. The premise of this repo is that infrastructure is described in the repository and applied from it; dashboards are the one surface that isn't.

Git Sync mirrors an instance, or a scoped folder within it, to a repository and records edits as commits.

## Scope

- Confirm Git Sync's status and requirements against the Grafana version actually running, before designing around it. It shipped experimental in Grafana 12, and "experimental" is a real constraint for something that owns dashboard state.
- Decide the scope of the mirror: the whole instance, or a folder holding the dashboards this repo owns.
- Decide the target repository — this one, or a dedicated dashboards repo.
- Decide the authoritative direction. Git-wins means UI edits are reverted on sync, which is the IaC-consistent answer and also the one that makes exploratory dashboard work annoying. Git-records means the UI stays authoritative and git is an audit log. Pick deliberately.
- Decide how this interacts with any dashboards already provisioned by other means, so the two don't fight.

## Acceptance criteria

- [ ] Git Sync's availability on the running Grafana version is confirmed, with the finding recorded either way.
- [ ] If adopted: a dashboard change appears as a commit.
- [ ] The authoritative direction is stated, not left ambiguous.
- [ ] Interaction with existing provisioning is resolved.

## Additional context

Closing this with "not available or still too experimental on our version" is a legitimate outcome, provided the finding is recorded. The fallback — dashboard JSON exported by a scheduled job — is a heavier and different design that deserves its own issue rather than being smuggled in here.

Source: a Grafana 12 release note highlight describing Git Sync mirroring an instance or a scoped folder to git.