Introduces a production Docker Compose stack that places nginx in front
of gunicorn. nginx serves the frontend SPA and Django static files
directly, and proxies all backend routes (/api, /admin, /healthz, etc.)
to the Django container. SECURE_SSL_REDIRECT is now env-configurable so
plain-HTTP nginx deployments work without separate settings files.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
