Docs: add reproducible uv setup using pinned Python 3.11.13

[VolodymyrLinuxovich]

Problem

The README currently lists Python 3.11+ and creates the virtual environment
using the user's default python executable. However, the repository pins
Python 3.11.13 in .python-version.

This makes the setup path ambiguous on systems where another Python version is
the default, and it does not show users how to reproduce the environment with
the version selected by the repository.

Proposed change

Add a recommended setup path using uv that:

• installs Python 3.11.13;
• creates .venv explicitly with Python 3.11.13;
• verifies the selected Python version; and
• installs the existing requirements.txt.

Keep the existing standard venv and pip instructions as an alternative.

I validated this setup from a clean environment on macOS using the repository's
current pinned dependencies.

[VolodymyrLinuxovich]

I'm working on this and will submit a documentation-only PR.