Add disposable VM deployment path

[nonprofittechy]

Summary

Adds a concrete production deployment path for running HaddenDraft on a disposable Ubuntu VM while moving secrets and durable state out of the VM.

Includes:

• production backend and frontend Dockerfiles
• nginx frontend/static/API proxy config
• production Docker Compose file
• Key Vault-backed env template
• deploy/bootstrap-vm.sh to bootstrap or redeploy a VM from scratch-ish Ubuntu host state
• DATABASE_URL support for external PostgreSQL while preserving local SQLite defaults
• production dependencies for gunicorn, psycopg, and WhiteNoise
• deployment documentation and README link

Notes

The bootstrap script intentionally avoids remote installer pipes. It installs common Ubuntu packages and docker.io, then fails clearly if the host still needs the Docker Compose plugin or Azure CLI installed by the VM build process.

Validation

• Compared branch against main; branch is 11 commits ahead and touches the expected deployment/config/docs files.
• Not run locally in this environment because I do not have a VM, Docker daemon, Azure CLI login, or Key Vault access here.