Introduce 3.13 and drop 3.8 Python image generation
### Python pre-releases
- [x] Use `rc` tag, unstable Python version
- [x] Introduce with `gcc` and `libffi-dev` installed in the meantime
- [ ] ~~Install `pre-commit` and `git` on `3.13` image.~~
### Python stable release
- [x] Remove `gcc` and `libffi-dev` once no longer necessary, once Py3.13 wheels are provided to run `poetry install`
- [x] Remove `rc` tag once Python 3.13 is released as stable
- [x] Drop Python 3.8 image generation
- [x] Use Alpine Linux, because Pendulum does not provide 3.13 wheels and Pendulum requires up-to-date Rust toolchain, which can be found in Alpine 3.20, but not in Debian 12. #11+
- [x] Remove Rust toolchain installation once Pendulum provides 3.13 wheels.
### ~~Default image usage switch?~~
- [ ] ~~Remove `pre-commit` and `git` installation from `3.12` image, once no longer default image in DuniterPy and Silkaj projects.~~
### Post
- [x] Create follow-up ticket for Py 3.14/3.9: #12+
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