* refactor(docker): rename server image to gateway
Rename Dockerfile.server to Dockerfile.gateway and update all image
references from openshell/server to openshell/gateway across Helm
charts, Kubernetes manifests, mise tasks, build/deploy scripts, CI
workflows, and documentation.
The underlying Rust binary (navigator-server) is unchanged -- this
rename only affects the Docker image name and Dockerfile.
* fix: catch remaining server->gateway references in docs and comments
Pass the computed cargo version through Docker and cluster packaging paths so deployed clusters report the built artifact version while keeping latest and explicit version tags aligned.