ci: publish remoteserver images to ghcr and docker hub

[ksaidi-terpomo]

Summary

• Add tag-driven Docker image publishing for the standalone remoteserver to GHCR and Docker Hub.
• Publish versioned multi-arch images only; no latest tag.
• Update Docker and remote-mode documentation around the standalone remoteserver and embeddable starter.
• Update compose files to use the postgresql profile and env-defaulted Postgres settings.

Image names

• ghcr.io/terpomo-io/pmitz-remoteserver:
• terpomo/pmitz-remoteserver:

Validation

• actionlint
• git diff --check
• Build workflow passed
• Remoteserver integration workflow failed after merge and needs follow-up