Added CHANGELOG entry documenting the aiohttp>=3.13.4 security constraint
that remediates CVE-2026-34513 and CVE-2026-34515 (high-severity open redirect
vulnerabilities). The dependency constraint was already present in pyproject.toml
via commit f0ff4bce on master; this PR documents it in the CHANGELOG and
closes the tracking issues.
ISSUES CLOSED: #1549, #1544