docs: note Python 3.14 support under [Unreleased]

Open the [Unreleased] section in CHANGELOG.md per Keep a Changelog
1.1.0 and record the new Python 3.14 support under ### Added.

Author: jcardozo-eth

CHANGELOG.md

@@ -5,6 +5,13 @@ All notable changes to this project are documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Added
+
+- Python 3.14 support: added to the CI matrix and to the `pyproject.toml`
+  trove classifiers.
+
 ## [3.0.1] — 2026-04-15
 
 ### Fixed