[egorsmkv]

Closes #30.

Extend the existing Windows x64 matrix with CPython 3.15, 3.14t and 3.15t while retaining 3.10–3.14. Allow prerelease interpreters for the upcoming 3.15 release.

Validate wheel filenames and internal WHEEL metadata against the exact interpreter/ABI/win_amd64 tag, confirm interpreter version, x64 architecture and free-threaded configuration, then install each wheel in a fresh venv and run all existing python/tests.

Run the Windows matrix on relevant pull requests; other packaging jobs remain tag/manual only and PyPI publishing remains tag only.

Validation completed on commit 2152cd0:

• Windows wheel CI: all eight Windows jobs succeeded; all artifacts uploaded.
• CPython 3.15.0rc3: fasttime_rs-0.3.0-cp315-cp315-win_amd64.whl; clean installation succeeded; 29 tests passed in 0.06s.
• CPython 3.14.8 free-threaded: fasttime_rs-0.3.0-cp314-cp314t-win_amd64.whl; clean installation succeeded; 29 tests passed in 0.07s.
• CPython 3.15.0rc3 free-threaded: fasttime_rs-0.3.0-cp315-cp315t-win_amd64.whl; clean installation succeeded; 29 tests passed in 0.04s.
• Existing CPython 3.10–3.14 Windows jobs also passed.
• Existing Test workflow: succeeded.
• YAML and inline Python syntax checks and git diff --check passed.

Python 3.15 validation currently uses RC3, not the final release. This PR does not publish packages.