Use Python type annotations

[feltech]

What

Use Python type annotations consistently across all files

Why

Type annotations make the code easier to understand for both devs and IDEs.

[foundry-markf]

I would also highly recommend as part of this, once type annotations are present, to have them checked for as part of CI, e.g. using mypy. I've seen that usefully spot issues before.

[Srish-ty]

@feltech @foundry-markf
I would like to work on this issue.
I'll raise the pr by EOD