feat: install api python package inside docker

Expect feat: install api python package inside docker, this MR doesn't introduce any behavior changes, and are mainly small cleanup/improvements.

• feat: use allowlist based .dockerignore
• feat: don't compile python byte code in docker
• feat: don't buffer stdout/err in docker
  This makes sure we don't loose any logs that might have been buffered and haven't been written to the docker logs.
• feat: disable pip cache during docker build
• feat: install api python package inside docker This mainly allow users to use the funkwhale-manage entrypoint.
• style: readability for docker pip dependencies install
• style: sort apk dependencies in docker
• feat: improve docker caching The apk dependencies will change less often than the venv from the builder.