Drop Python 3.8- support, add Python 3.9+ support, support the upcoming version of frontera

[Gallaecio]

No description provided.

[Copilot]

Pull Request Overview

This PR drops support for Python 3.6–3.8, adds Python 3.9+ support, updates dependencies (including an upcoming Frontera version), bumps the package version, and refreshes CI tooling.

• Update tox and GitHub workflows for Python 3.9–3.13
• Bump version to 0.5.3, add bumpversion config in pyproject.toml
• Introduce _now() for timezone-aware timestamps and handle byte-fingerprint serialization

Reviewed Changes

Copilot reviewed 15 out of 15 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
tox.ini	Remove old Python envs, add py39–py313
setup.py	Bump version to 0.5.3, adjust dependencies
pyproject.toml	Add bumpversion config and pytest filterwarnings
hcf_backend/backend.py	Add _now() helper, timezone-aware created_at, byte fingerprint handling
CHANGES.rst	New changelog entry for upcoming release

Comments suppressed due to low confidence (1)

hcf_backend/backend.py:273

• This new branch handling byte-fingerprints isn’t covered by existing tests. Add a unit test that exercises fp of type bytes to ensure correct hex decoding.

if ( qdata["request"]["meta"].pop(b"_hcf_backend_fp_type", None) == "bytes" ):