Add more filters to the reruns page

_Generated by an AI assistant on behalf of @rpbritton._

### Problem statement

Raised as an action item in the Charm QA Triage Retrospective (9 Sept 2026). The reruns page currently has limited filtering, making it hard to find specific queued/requested reruns when there are many in flight.

### Proposal

Add more filter options to the reruns page, for example:

- Environment (name/substrate)
- Artefact (name/version)
- Family (e.g. charm/snap/deb/image)
- Status/priority of the rerun request

Suggestions welcome from maintainers on which filters are most useful given the underlying data model.

Start at the reruns page and inspect the underlying data model to determine which fields can support filtering. Review the proposed environment, artefact, family, status, and priority dimensions, then confirm with maintainers which filters are in scope; done means the selected filters work for finding queued or requested reruns.

Written by the indexing model from the issue text.