CI: copy central LICENSE into package directories before build

[paul-gerber-svg]

Previously, the python build backend failed to include the LICENSE file
in sdist and wheel distributions because build processes run isolated
within subpackage directories (./sdk and ./compliance_tool) without
access to the root LICENSE file.

Now, the CI workflows (pr.yml and release.yml) copy the root LICENSE file
into the respective package directories immediately before executing
python -m build, ensuring correct metadata inclusion for PyPI releases.

Fixes #462

[s-heppner]

I guess the Python package server is being built in this action? In that case, we should also include the LICENSE file there.

[paul-gerber-svg]

I checked the workflows and Dockerfiles for server:

• server isn't packaged or published as a standalone Python distribution (sdist/wheel) to PyPI like sdk and compliance_tool. It is built exclusively as a Docker image.
• In .github/actions/build-server/action.yml, the Docker build context is set to the repository root (context: .), so Docker already has full access to the root LICENSE file if needed.
• The Dockerfiles explicitly copy only ./server/app and ./server/pyproject.toml, so executing cp LICENSE server/ in CI would be ignored by the Docker build anyway.

Therefore, no cp LICENSE step is required for the server build.

[hpoeche]

I recently had to deep-dive in setuptools configuration options and came across this. We should consider here, that the way we define the license in our pyproject.toml files is deprecated. More information and migration guide can be found here: https://setuptools.pypa.io/en/latest/userguide/license_migration.html

Additionally, I personally would prefer symlinks over copying files in CI, if this is not already an option you considered.