feat(migrate): containr migrate railway — GraphQL import of services/vars/domains (#51)

--token (or RAILWAY_TOKEN) reads the Railway project via backboard
GraphQL: services resolve to git-repo or image services with command +
replicas, variables and service/custom domains follow. --dry-run prints
the plan; --into targets an existing project. Both account (Bearer) and
project tokens (Project-Access-Token header) work.

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Co-authored-by: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

docs/guides/CLI.md

@@ -74,6 +74,7 @@ import compose <project-id> <compose.yml|->
 nodes list|get|delete|tokens     node agents + onboarding tokens (admin)
 nodes add <user@host>            SSH bootstrap — one session installs the agent, then never needed again (--print for manual runs)
 nodes update|prune|commands      rename/auto-prune, bounded docker prune, command history
+migrate railway                  pull a Railway project (services, vars, domains) via GraphQL and recreate it — --dry-run prints the plan
 scaling status|policies|services|scale
 ha status|alerts|health|policies|enable|disable|failover
 security scan|vulnerabilities|metrics