In deployments use .env file consistent

[sverhoeven]

In deploy/arq/ a .env file is used but not configured in compose file
In .devcontainer/ a .env file is used in webapp service, but you do own npm run dev so env is from that terminal.

Each compose file should in the webapp service have a section

    env_file:
      - path: .env
        required: false

And documentation should point the /.env.example as a starting point.

[sverhoeven]

In

haddock3-webapp/deploy/arq/docker-compose.yml

Line 28 in df7d90a

- HADDOCK3WEBAPP_REFRESH_RATE_MS

and var in .env file is passed through. If this line does not exist the var is also not set in the container.

Instead of repeating the var name, we should use the env_file section to pass through all vars set in the .env file.

[sverhoeven]

Also would be nice to make sure that any env var used in the code is documented either in .env.example or the docs/ .