246 devops fully migrate to pyprojecttoml

[enrico-lattuada]

Description

• Remove existing setup.py
• Improve the pyproject.toml to include a CMake backend (e.g., scikit-build-core)

Motivation and context

The setup.py framework is outdated, and pyproject.toml (with modern tools) can do the same job with less maintenance effort.

Resolves #246

How has this been tested?

• CI pipelines
• Locally by running tests after installation with:
  • Arch Linux (Linux 6.14.9), in virtual environment, using gcc 15.1.1, cuda 12.8, with cuda enabled
  • Windows 11, in both global and in virtual environment (conda), using visual studio compiler, cuda 12.9, with cuda enabled

Change log

v0.3.14 (2025-MM-DD)
^^^^^^^^^^^^^^^^^^^^

*Changed*

- Migrated build system from ``setup.py``/``setup.cfg`` to [PEP 517/518] ``pyproject.toml`` standard.
- ``pybind11`` is now a build dependency and is no longer included as a static copy in the external lib directory.

*Removed*

- Removed statically saved ``pybind11`` from the external lib directory 

Checklist:

• I have reviewed the Contributor Guidelines.
• I agree with the terms of the FastDDM Contributor Agreement.
• My name is on the list of contributors (docs/source/credits.rst) in the pull request source branch.

[krauthex]

Thank you very much @enrico-lattuada for your efforts! The changes look good to me, at least as far as I understand CMake ;-) Making pybind11 an install dependency definitely is the much cleaner approach.

The base branch was changed.

[eXpensia]

Except this minor changes it's clean!