* Rewrite .golangci.yaml to v2 schema: linters-settings ->
linters.settings, issues.exclude-rules -> issues.exclusions.rules,
issues.exclude-dirs -> issues.exclusions.paths
* Drop deprecated revive exported/package-comments rules: personal
project, not a public library; godoc completeness is not a CI req
* Add //nolint:gosec G101 on PassphraseEnv default in config.go:
environment variable name is not a credential value
* Add //nolint:gosec G101 on EventPGCredUpdated in model.go:
audit event type string, not a credential
Security: no logic changes. gosec G101 suppressions are false
positives confirmed by code inspection: neither constant holds a
credential value.
