Move to uv.

[stankudrow]

Features:

• abandon pdm in favour of uv
• add Python3.14 support
• move from Makefile to Justfile -> https://github.com/casey/just
• update GHA workflow files
• some other chores

Based on the discussion from the #218 .

[stankudrow]

@Tinche , hello.

Do you need tox for this project if GHA are enabled? If not, I'll remove "tox.ini" file.

[Tinche]

I'd prefer to keep tox since it can be useful to run a multitude of tests locally for contributors

[stankudrow]

Maybe to do something with the following lines in conformance with uv GHA integration.

[stankudrow]

@Tinche , hello.

I need your coauthorship with GHA and tox's runner option.

[Tinche]

Thanks for your efforts Stanley. This turned out to be significantly trickier than I assumed it would. Still not super happy with how the Justfile had to change, but I think this is an issue with tox-uv.

[stankudrow]

Thanks for your efforts Stanley. This turned out to be significantly trickier than I assumed it would. Still not super happy with how the Justfile had to change, but I think this is an issue with tox-uv.

Thank you in helping to finish this PR, I learnt more about tox, good experience.