Replace the minimal placeholder .env.example with a comprehensive template
documenting every variable consumed by docker-compose.yaml, organized by
service (Django core, HTTP, Postgres, Neo4j, Memcached, S3/MinIO, Daedalus,
Celery/RabbitMQ, etc.). Clarifies that this file is rendered from an Ansible
Jinja2 template with vaulted secrets in production, and distinguishes it
from the in-tree mnemosyne/.env used for bare-Python development.
Reorganize Docker Compose services: the Django/gunicorn container is now
`app` and nginx is `web`, better reflecting their roles. Add a dedicated
gunicorn configuration and install curl in the runtime image for health
checks.
Update documentation to reflect:
- Neo4j migration from ariel.incus to a dedicated umbriel.incus instance
- Rationale for requiring a dedicated Neo4j instance (single-tenancy
assumptions, label/index isolation, schema ownership)
- New service naming in compose commands and log tailing examples
