Version 1.7.4. Lots of bugfixes.

Version 1.7.4:

• Convert setup.py to pyproject.toml as primary metadata source (PEP 621)
  • All package metadata now lives in pyproject.toml [project] table
  • setup.py reduced to C++ extension compilation only
  • Supports uv build (uv build) as well as pip/build
  • Remove superseded necpp/setup.cfg
• Fix #24: VSWR formula guard — add explicit np.abs() in vswr() to prevent negative values
• Fix #8: Add missing handle_nec method to necpp/tests/test_multiple_sc_cards.py
• Fix #31: Guard numpy import in PyNEC/setup.py with try/except for PEP 517 metadata phases
• Fix multiple bugs found during code analysis:
  • Move test_multiple_sc_cards.py from PyNEC/tests/ to necpp/tests/ (it imported the wrong module)
  • Fix setup.cfg referencing nonexistent README.txt → README.md
  • Fix broken nosetests command in build_wheels.sh
  • Fix double-space in CI CIBW_BUILD string
  • Fix license metadata consistency (GPLv2 → GPLv3) in both setup.py files
  • Fix hard-coded swig3.0 → swig in necpp/build.sh
  • Fix symlink creation failure on re-run in both build.sh scripts
  • Fix typo (stop_ → stop) and unassigned delta bug in context_clean.py Range class
  • Add clarifying docstring for ex_card overload in nec_context.i
  • Add scipy, matplotlib to dev-requirements.txt
  • Remove stale Python 2 classifiers from necpp/setup.py
  • Fix Makefile manylinux2014 → manylinux_2_28
  • Fix CI branch filter (main → master)