Create quickstart workload release pipeline

Stand up the CI + release pipeline for the new quickstart workload so it
builds, packs, and publishes to the workloads feed independently of the
core CLI release cadence.

## Definition of Done

- [ ] Public-build pipeline runs on PRs touching the quickstart workload.
- [ ] Official/signed-build pipeline publishes the quickstart workload
nupkg to the workloads feed on release.
- [ ] Pipeline ownership documented (CODEOWNERS or pipeline description).
- [ ] A test release produces an installable package consumed by
`func workload install quickstart`.

Locate the existing public-build and official/signed-release pipeline definitions, then find the quickstart workload packaging entry point. Compare the current CLI release flow with the independent workload requirements and verify ownership documentation. Done means PR builds run, a signed release publishes an installable nupkg to the workloads feed, and `func workload install quickstart` consumes a test release.

Written by the indexing model from the issue text.