v0.5.2 — Python 3.11–3.14 support + CI matrix

- requires-python broadened to >=3.11 (was >=3.14)
- Removed cascache_server optional dependency group (blocked older Pythons)
- GitLab CI test jobs now run as a 4-version matrix (3.11, 3.12, 3.13, 3.14)
- build job needs updated to reference all 12 expanded matrix job names

See CHANGELOG.md for the full list of changes.