DOC: update installation page

[lucascolley]

We just overhauled the SciPy installation page at https://scipy.org/install/, including:

• creating a separate beginner guide for those who may not be comfortable with using a terminal or happy to learn to use a package manager
• recommending project-based workflows to users who do not consider themselves beginners (uv and pixi)
• modernising instructions for installing with pip or conda

You may wish to do similar things for https://numpy.org/install/. Feel free to copy anything I wrote on the SciPy page!

[mattip]

It might be nice to set this up as a tab-based page with a tab for each installation method. This would emphasize that they are equivalent alternatives.