MAINT: update anaconda=2025.06

[mmcky]

This PR updates to anaconda==2025.06 and python=3.13

[mmcky]

The change to python=3.13 is going to be an issue due to deprecation of imghdr https://docs.python.org/3/library/imghdr.html

• update to jupyter-book==2.0 or update jupyter-book==1.0.3 for now.

[mmcky]

There are a lot of software conflicts that we will need to fix

  The conflict is caused by:
      jupyter-book 1.0.4.post1 depends on sphinx~=7.0
      sphinx-togglebutton 0.3.2 depends on sphinx
      quantecon-book-theme 0.8.2 depends on sphinx<6 and >=5

• update quantecon-book-theme to be compatible with sphinx~=7.0

[mmcky]

Closing in favour of #364