Drop Python 3.8 support

[akx]

Python 3.8 has been EOL for 9 months.

Previous versions of valohai-cli will of course continue to work with Python 3.8.

[Copilot]

Pull Request Overview

Modernizes the codebase by dropping Python 3.8 support and adopting Python 3.9+ typing syntax features. This change aligns with Python 3.8 being end-of-life for 9 months and allows the use of more concise type annotations.

Key changes:

• Replaced legacy typing imports with built-in generic types (e.g., List[T] → list[T])
• Moved collections types to collections.abc module
• Added from __future__ import annotations for forward compatibility
• Updated development environment configuration

Reviewed Changes

Copilot reviewed 57 out of 57 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
pyproject.toml	Updated minimum Python version requirement from 3.8 to 3.9 and ruff target version
.pre-commit-config.yaml	Updated pre-commit hook versions for ruff and mypy
.github/workflows/ci.yml	Removed Python 3.8 from test matrix and updated Ubuntu version to 24.04
valohai_cli/**/*.py	Modernized type annotations throughout codebase using Python 3.9+ syntax
tests/**/*.py	Updated test files with modern type annotations
scripts/ensure_click_help.py	Applied type annotation modernization to utility scripts

[teroyks]

Slowly moving towards modern code! 👍
(Even borrowing more modernity from the future!)

[teroyks]

@akx for some reason, there are still a couple of Ubuntu 22 checks pending, even though that was removed from the test matrix. Leftovers from some earlier push?

[akx]

@akx for some reason, there are still a couple of Ubuntu 22 checks pending, even though that was removed from the test matrix. Leftovers from some earlier push?

Ah, no, it's just that the "required checks" specified in the repo settings refer to versions too (which makes sense), so those are left pending until I :cattunk: the settings