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

--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.

Generated with [Devin](https://devin.ai)

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

app/backend/internal/cli/root.go

@@ -94,6 +94,7 @@ func init() {
 	rootCmd.AddCommand(commands.BannersCmd)
 	rootCmd.AddCommand(commands.InvitesCmd)
 	rootCmd.AddCommand(commands.UpCmd)
+	rootCmd.AddCommand(commands.MigrateCmd)
 }
 
 func initConfig() {