Support compose user: directive as k8s runAsUser

Read the user: field from compose service definitions and map it to
securityContext.runAsUser on the k8s container spec. Needed for init
containers using images that run as non-root by default (e.g.
bitnami/kubectl runs as UID 1001).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

stack_orchestrator/deploy/k8s/cluster_info.py

@@ -567,6 +567,7 @@ class ClusterInfo:
                     volume_mounts=volume_mounts,
                     security_context=client.V1SecurityContext(
                         privileged=self.spec.get_privileged(),
+                        run_as_user=int(service_info["user"]) if "user" in service_info else None,
                         capabilities=client.V1Capabilities(
                             add=self.spec.get_capabilities()
                         )