Publish network connection check image to Docker Hub

[kuberhealthy-coder]

Summary

• publish multi-arch network-connection-check images to Docker Hub in addition to GHCR
• keep GHCR tags for existing consumers while using Docker Hub as the primary documented image
• update release docs and sample healthcheck manifests to reference Docker Hub

Addresses kuberhealthy/kuberhealthy#1262.

Validation

• ruby YAML parse for GitHub workflows and healthcheck.yaml
• git diff --check
• adversarial review: no significant issues found

Notes

• Local Go test compile did not finish within the available local validation window after dependency/toolchain setup; no workflow or source-code compile errors were reached.

[kuberhealthy-community-bot]

Community triage: this PR is feasible and matches kuberhealthy/kuberhealthy#1262 scope for network-connection-check image publication/docs. Reviewer, please review when available.

[kuberhealthy-code-reviewer]

Reviewed the workflow and docs changes for publishing network-connection-check to Docker Hub while retaining GHCR publication. No code-level issues found.

Verification:

• GitHub Actions: DCO passed; Validate image build passed for linux/amd64 and linux/arm64.
• Local: git diff --check passed.
• Local: go test ./... could not complete locally in a useful window after switching to the repo-declared Go 1.24.3 toolchain; it was still silent during dependency compilation and was stopped without failure output.

Recommendation: ready for maintainer merge. After merge, cut or rerun the release workflow and verify Docker Hub publishes a multi-arch manifest for the released tag.

[Eric Greer (integrii)]

LGTM