Add ruff rules to enforce typing annotations

[Lotram]

Add ruff rules ANN to ensure all functions are annotated, improving typing coverage.

First commit enforces this everywhere except services/ ( + docs/ and tests/, already excluded from type checking).

Second commit enforces it in services/__init__.py + 2 services, as an example

[ryneeverett]

Does annotating all functions necessarily improve typing coverage (as enforced by ty)? Doesn't ty complain if it can't infer a type?

[Lotram]

Doesn't ty complain if it can't infer a type?

Not really, all missing annotations are replaced by Unknown, an implicit equivalent of Any (see ty doc)

See for example this piece of code:

def f(a):  # expects str
    a.splitlines()


def g():
    b = 5
    return f(b)

without type annotation, ty (as well as pyright and mypy) won't find any issue.

whereas

def f(a: str) -> list[str]:  # expects str
    return a.splitlines()


def g():
    b = 5
    return f(b)

raises an error with both ty and pyright (strangely, mypy does not raise anything with the default config, I haven't investigated)

All type checkers require type annotations to be fully working. Both mypy and pyright have settings to enforce this, Astral uses ruff rules for that