chore(images): migrate base images to private -stable aliases

[dliub]

What

Re-homes base images to Hasura's private Artifact Registry us-docker.pkg.dev/hasura-container-images/external-images via floating -stable aliases. The -stable aliases auto-advance to the latest patched digest within the same version line, so this keeps the same version while satisfying the policy that all containers deployed in Hasura infra are pulled from the private registry rather than upstream registries.

Exact FROM swaps

Dockerfile

• FROM golang:1.26 → FROM us-docker.pkg.dev/hasura-container-images/external-images/docker.io/library/golang:1.26-stable

Notes

• This is part of an org-wide Phase 1 migration: exact-match swaps only. No version bumps, no reformatting, no other lines touched.
• The gcr.io/distroless/static-debian13:nonroot stage was intentionally left unchanged — it is not part of this scoped swap list.

🤖 Generated with Claude Code

[github-actions]

Package	Line Rate	Health
github.com/hasura/ndc-prometheus/connector/api	76%	✔
github.com/hasura/ndc-prometheus/connector/client	64%	➖
github.com/hasura/ndc-prometheus/connector	64%	➖
github.com/hasura/ndc-prometheus/connector/internal	66%	➖
github.com/hasura/ndc-prometheus/connector/metadata	89%	✔
Summary	72% (3531 / 4923)	✔

Minimum allowed line rate is 40%

[dliub]

Closing as out-of-scope: this PR came from an exploratory org-wide base-image -stable migration sweep that we've scoped down to PromptQL self-hosted images only. Reopen if needed.