Reduce Docker container size

[Shadowsith]

These changes optimize the size of the docker container based on #745

Before with python:3.12-bookwom: ~1.09 GB

After the changes: ~276 MB

How I've tested it:

1. Installed client npm dependencies and built client in project with production api environment
2. Created a docker-compose.yml in project root folder to build/test the local spoolman image
3. Tested Dockerfile changes via docker-compose build
4. Started container via docker-compose up -d and made some user tests within the web client

My local docker-compose.yml as reference

version: '3.8'
services:
  spoolman:
    image: spoolman
    container_name: spoolman
    restart: unless-stopped
    volumes:
      # Mount the host machine's ./data directory into the container's /home/app/.local/share/spoolman directory
      - ./data:/home/app/.local/share/spoolman
    ports:
      # Map the host machine's port 7912 to the container's port 8000
      - "7912:8000"
    environment:
      - TZ=Europe/Stockholm # Optional, defaults to UTC
    build:
      context: .
      target: python-runner
``

[jpiccari]

You've done great getting the docker image much smaller. You can get it a bit slimmer by moving this build to the builder stage and using COPY --from=python-builder to get just the resulting binary. This allows you to avoid curl, gcc, and libc-dev dependencies.

I'm seeing built image size of ~253MB with those changes. Not nearly the gain you already achieved but I'm more interested in avoiding having dev tools in my images.

[Donkie]

the dependencies are removed at the last line, apt-get purge

[jpiccari]

Since this uses multi stage builds, I think you can use the non-slim image here. It won't affect the final image and includes some dependencies you might otherwise need.

[Donkie]

I think it's good practice to have the same base image in both the builder and runner, both so that they share the same base and dependencies, and it reduces the number of images you need to download

[Donkie]

I hijacked your PR a bit, but I've fixed some issues and minimized the final docker image as much as possible.
Thanks for the contribution, and sorry for the delay!