build: enable Go FIPS profile

[omercnet]

Summary

• switch the manual Docker build to Verity's pinned Go 1.26 FIPS builder
• pin Go FIPS builds to GOFIPS140=v1.0.0 and enable GODEBUG=fips140=on for release/manual builds
• expose GODEBUG=fips140=on and GOFIPS140=v1.0.0 in the runtime image and k8s deployment

Aligned with Verity FIPS hardening in verity-org/verity#541.

Validation

• make build
• docker build -t pgpeek:fips-test .
• make test
• go version -m ./pgpeek shows DefaultGODEBUG=fips140=on and GOFIPS140=v1.0.0-c2097c7c
• docker image inspect pgpeek:fips-test shows GODEBUG=fips140=on and GOFIPS140=v1.0.0
• kubectl kustomize k8s/ renders GODEBUG=fips140=on and GOFIPS140=v1.0.0
• runtime smoke with disposable Postgres: /healthz returned 200 ok

Note: goreleaser is not installed in this local environment; config validation will run in CI via the existing pinned goreleaser action.