Introduces an `x-infrahub-config` extension field to the docker-compose file. This block aggregates all Infrahub environment variables (AWS, DB, Broker, Cache, etc.) into a reusable anchor (`&infrahub_config`).
This change allows for:
- Centralized management of configuration options.
- Improved visibility of available settings matching the official documentation.
- Easier injection of these variables into dependent services via the new anchor.
