fix: bake version into Docker image at build time

- Add VERSION build arg to Dockerfile
- Pass --build-arg VERSION in release workflow
- Remove VERSION env override from docker-compose files
- Version is now immutable inside the image, no runtime env var needed

docker-compose.yml

@@ -20,7 +20,6 @@ services:
     env_file:
       - .env
     environment:
-      VERSION: ${AOC_VERSION:-dev}
       MONGO_URI: mongodb://${MONGO_ROOT_USERNAME}:${MONGO_ROOT_PASSWORD}@mongo:${MONGO_PORT}/
     depends_on:
       - mongo