[change] Update tested versions

[adamchainz]

Checklist

• I have read the OpenWISP Contributing Guidelines.
• I have manually tested the changes proposed in this pull request.
• I have written new test cases for new code and/or updated existing tests for changes to existing code.
• I have updated the documentation.

Reference to Existing Issue

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Description of Changes

Make these version changes:

1. Add Python 3.13.
2. Add Django 5.2 (currently in beta, expected April).

Also:

1. Declare the the Django version dependency in setup.py.
2. Update openwisp-utils to install from GitHub’s tarball URLs. The lack of suffix caused issues for me with uv via tox-uv.
3. Drop parallel testing - it was slower for me, 2s versus 1s.

Screenshot

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[adamchainz]

Sigh... the install step is broken on Python 3.13 because coveralls pins to Python <3.13 and hasn't removed that yet. Pending PR: TheKevJames/coveralls-python#542 .

I didn't see this locally because I use tox with uv, via tox-uv. They deliberately ignore upper version bounds on Python: astral-sh/uv#4022 . Would you be interested in converting the testing to uv? It wouldn't take much more than installing tox-uv.