Run Mypy by default.

[Carreau]

Otherwise the types annotations are less usefull, even with ruff.

Ignore/fix types errors.

Also the mypy config was way to lax, ignoring errors project wide intead of per-file. This make it much stricter and only ignore error on each file, so this types of errors are still confined, and it is easy-ish, to make it a bit more stricter progressively

[Carreau]

I'm still also super-confused as running mypy directly and running via hatch/precommit gives different results