Python templates: Add dev setup (linter, type checker, tests)

[vdusek]

Context

In the context of AI-assisted development, a fast feedback loop is essential for coding agents. When an agent writes code, it needs immediate signals about correctness — type errors, lint violations, test failures — to iterate effectively.

JS/TS Actor templates already provide this through dev dependencies: type checking, linting, etc. Python templates currently lack any dev setup, partly because they only use a plain requirements.txt with no concept of dev dependencies.

Goal

Add a proper development setup to Python Actor templates, including:

• Linter — e.g. Ruff (covers both linting and formatting)
• Type checker — ty (from the Astral ecosystem, pairs well with Ruff)
• Configuration — pyproject.toml with sensible defaults for all tools
• Test setup — basic pytest configuration so users (and agents) can write and run tests out of the box

This would bring Python templates closer to parity with JS/TS templates in terms of developer experience and make them significantly more useful in AI-assisted workflows.

Notes

• This is related to Python Actors: Add option for using uv setup #350 — supporting uv (or another modern package manager) would make it much easier to manage dev dependencies separately from production dependencies
• The dev setup configuration should follow conventions already established in Crawlee for Python

Parent issue

Sub-issue of https://github.com/apify/apify-core/issues/25871