docker (re)build should run 30 seconds MAX

[Decappi]

User story

1. As a developer
2. I want a snappy docker build process, the build process should only take long if it's the first time
3. So that I can have fast feedback loops in my development process

Acceptance criteria

• docker compose up --build takes no more than 20 seconds
• all permanent changes to the container happen before the container is started

Definition of done

• Code was reviewed by another person
• GitHub CI runs successfully
• Feature is merged into main branch

[oliviadargel]

This will be impossible in case no model is trained locally as the training is then called on container start up