Add blog post images to source code

[nikwen]

Most images in our blog posts currently have URLs like the following:

https://github.com/user-attachments/assets/3ec6c87b-1569-443b-8b63-eb20ee4fd96b

We should not rely on GitHub for image hosting.
Instead, we should add images to the /static/assets/img directory.

We should do this going forward, but we should also download all of our existing images and add them to the source code so that we don't lose them.