Add official support for Python 3.14 #2686

Summary

Python 3.14 is already exercised in the nightly/full CI matrix (see #2531), but the agent does not yet declare official support:

• setup.cfg PyPI classifiers stop at 3.13
• docs/reference/supported-technologies.md lists up to 3.13
• PR CI matrix (.ci/.matrix_python.yml) still uses python-3.13 as the newest version
• .ci/publish-aws.sh does not list python3.14 as a Lambda compatible runtime

Proposal

Mirror the approach from #2265 (official Python 3.13 support): update packaging metadata, documentation, PR matrix, and Lambda publish script to declare Python 3.14 as supported.

Notes

• Full-matrix 3.14 exclusions are already in .ci/.matrix_exclude.yml
• Known flake: Flaky kafka-newest test on 3.14 #2630 (kafka-newest on 3.14)

I plan to submit a PR for this shortly.