fix: support Python 3.14 core installs

[sidmohan0]

What changed

• Removed the package-wide Python <3.14 upper bound and declared Python 3.14 in package classifiers.
• Added Python 3.14 core and CLI coverage to CI.
• Made Python 3.14 core and CLI tests a release publishing gate.
• Aligned legacy setup metadata and documented the certified support boundary.

Why

PyPI metadata for DataFog 4.8.0 rejects Python 3.14 even though the lightweight core runs successfully on that interpreter. The upper bound prevents normal installation before DataFog code is evaluated.

Python 3.14 support is certified for the core SDK and CLI. Optional profiles remain dependent on upstream package availability and are not newly certified by this change.

Closes #171.

Validation

• Python 3.14.5 release-gate test selection: 597 passed, 12 skipped, 19 expected failures
• Python 3.14 core install-profile smoke test: passed
• Python 3.14 CLI install-profile smoke test: passed
• Built wheel metadata: Requires-Python: >=3.10 and Python 3.14 classifier present
• Clean Python 3.14 wheel install and scan/redaction smoke test: passed
• pre-commit run --all-files: passed