feat: add deploy workflow for reference-server container

[aditya-damerla128]

Summary

• Adds automated deployment workflow for the reference-server container
• Triggers on pushes to main affecting reference-server/** or clients/typescript/**
• Uses same SSH action pattern as the existing deploy-demo.yml

Setup Required

Before merging, add these GitHub secrets:

• REFSERVER_HOST - set to ozwellai-reference-server.opensource.mieweb.org
• REFSERVER_USER - deployment username (e.g., adamerla)

On the reference-server container:

• Add the SSH public key (from SSH_PRIVATE_KEY) to ~/.ssh/authorized_keys

Test plan

• Add GitHub secrets REFSERVER_HOST and REFSERVER_USER
• Add SSH public key to reference-server container
• Merge PR and verify workflow runs successfully
• Check PM2 status on reference-server after deploy

Closes #48