ci: drop dead golint step, align Go to go.mod 1.25, bump checkout to v4

[Bonny07]

What

A few CI housekeeping fixes:

• Remove the dead golint step — ci.yaml installed golang.org/x/lint/golint but never invoked it, and golint has been deprecated/frozen since 2021.
• Align the CI Go version to go.mod — the workflows pinned 1.24.2 while go.mod and the Dockerfile are on 1.25; bump them to 1.25.
• Bump actions/checkout@v3 to v4 in ci.yaml and docker.yaml (release.yaml was already on v4), off the deprecated Node 16 runtime.

Test

• All three workflow files parse as valid YAML.
• No build or runtime code touched.

[Bonny07]

Gentle bump on this — it's CI-only (drops the archived golint install step that no longer runs, aligns the workflow Go version with go.mod's 1.25, and bumps actions/checkout to v4), and it's been green since early June. No rush, merge whenever suits you.

Related: I opened #229 adding a hermetic unit-test suite for the translate package (the repo had none). With that in place, wiring go vet + gofmt gates into CI becomes worthwhile — happy to send that as a small follow-up.