Add Python 3.14 compatibility

[nikolaymatrosov]

Currently, the package metadata specifies support up to Python 3.13:

classifiers = [
    "Programming Language :: Python :: 3.9",
    "Programming Language :: Python :: 3.10",
    "Programming Language :: Python :: 3.11",
    "Programming Language :: Python :: 3.12",
    "Programming Language :: Python :: 3.13",
]

With Python 3.14 now available, installation and usage may be blocked or untested in environments that default to 3.14.

Request

Please:

1. Add Python 3.14 to the supported classifiers
2. Run CI against Python 3.14
3. Confirm compatibility or document any blockers