Expose network logs (HAR) as a downloadable artifact in the REST API

Network log collection works great — the HAR files are exactly what we need. The problem is they're only reachable by clicking through the web app (Details → Download network logs), so they can't be used in any automated pipeline.

Please expose the HAR through the API the same way DOM snapshots and run logs already are: an entry with kind: "network_logs" in GET /api/v2/testruns/{id}/debug-artifacts/, with the same pre-signed file + expirationTime shape. A direct route mirroring /logs/ would be a bonus, as would the equivalent for suite runs.

No new data collection is needed — the file is already produced and stored. Today debug-artifacts returns only dom_snapshot and logs, and every plausible artifact type for the network log 404s.

Our use case: we track front-end performance budgets (API latency, transfer size, request counts) on top of our nightly regression suites. The HAR already contains everything we need, but with the file available only through the web app we can't automate the check.