Refidxdb

New functions for handler. And make it easier to access the private `_source` property.

Introducing a handler that takes a URL argument.
Move the project to use [Pydantic](https://docs.pydantic.dev/latest/), which makes typing stricter!

Use `hatchling` instead of `pdm` for building

It is complicated to maintain two dev environments, both with nix and
poetry.
The switch was made to uv, since it uses the default dependency style,
it is faster and out of the box compatible with pyproject.nix.
With pyproject.nix only a pyproject.toml file needs to be provided and a
devshell will be created with all needed dependencies loaded from
nixpkgs!

No significant changes otherwise!

Add data explorer using streamlit
New refidx parsers
Aria is more stable