Improvements to development environment / cycle

A pull request for this has already been merged.

• #4529 by @henrikmidtiby — merged

There are a bunch of things that would be nice to get done until the next release to ensure a smoother dev experience with less friction when it comes to the releases and the changelog.

- [x] Switch project management tool from `poetry` to `uv`. As we are now recommending our users to use `uv` for their installation, it only makes sense to change our dev environment as well.
- [x] Check that lower bounds for required versions are actually sufficient for our direct dependencies. All issues that are reported with the new release are effectively a consequence of this: we don't notice this in fresh environments, but if users install Manim to their existing environments, we might end up with some packages that formally satisfy our version bounds, but are effectively too old.
- [ ] Release changelogs: to make editing them more straightforward, we could move them to GitHub. Advantage: the automatically generated ones are very nice, and could even be processed by a script to fix categorization + links to the docs. At the same time, producing links to the reference manual is way more convenient with the current Sphinx setup. We should discuss this some more. Ideally, it should be a matter of an hour or two to fully prepare a small / bugfix release.
- [ ] Make sure that the release process is properly documented in our wiki, including pre- and postprocessing steps.

No specific files or tests are named. Start by reviewing the current Sphinx release and changelog workflow, then inspect the wiki process for pre- and post-release steps. The issue is complete when the changelog approach is agreed and the release process is documented end to end.

Written by the indexing model from the issue text.