Deploy train: container name conflict and workers build failure (2026-10-14)

Imported from GitHub issue El-SaMa/oma#235 by @El-SaMa.

Two failed runs: 29baa0d8 'container name /oma-api-gateway is already in use' after removing MCP containers, then 62e84037 'target workers: failed to solve' at FROM node:22-alpine. The next run succeeded. Make the train remove stale named containers before recreate and retry a base image pull once. Log: /var/lib/oma-deploy-train/last-deploy.log.