cffi v2.0.0b1

What's Changed

• Add Python 3.14 support.
• Add CPython free-threaded support (3.14t+ only).
• Drop Python <= 3.8 support.
• Fix order dependency affecting nested type size calculation (#148).

Full Changelog: https://github.com/python-cffi/cffi/compare/v1.17.1...v2.0.0b1