uv-managed .venv environments may have pip disabled (PEP 668 / uv's
default hardening).  Running `python -m pip install` inside such a venv
raises a CalledProcessError even though uv itself is available.

Introduce `_resolve_pip_cmd()` which checks `shutil.which("uv")` at startup:

- uv found  → use ["uv", "pip"] (uv auto-detects the active venv)
- uv absent → fall back to [_PYTHON, "-m", "pip"] (no regression)

All pip invocations in `_bootstrap()` and `_install_commands()` now use
`_PIP_CMD` instead of the hard-coded `[_PYTHON, "-m", "pip"]` prefix.

On Windows, npm is installed as npm.cmd rather than a plain executable.
subprocess.run(['npm', '--version']) without shell=True raises
FileNotFoundError, causing the Node.js detection step to always report
npm as missing even when it is properly installed.

Reuse the existing _get_npm_command() helper (which already returns
npm.cmd on Windows) for the version-detection call, consistent with
how npm is invoked later during npm install.

…indows

fix: use npm.cmd for version detection on Windows

fix(scripts): prefer uv pip over python -m pip in start_tour.py

docs: add Polish translation of README