Add OPENSHELL_SANDBOX_IMAGE_PULL_POLICY env/CLI flag that propagates
through Config -> SandboxClient -> pod spec generation. When set, the
policy is applied to both inline and pod-template sandbox containers.
Helm chart exposes server.sandboxImagePullPolicy (default empty = K8s
default behavior). cluster-deploy-fast sets it to Always so dev
clusters always pull fresh sandbox images.
* 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
Drew Newberry