Support python 3.13 and 3.14, abandon 3.9

[ianbulovic]

3.14 is out, and 3.9 is EOL. Large diff, but only a few changes (diff is mostly the updated uv lockfile):

• Pin transformers to 4.56.1
  • Later versions add a new all_tied_weights_keys model attribute—we can probably support this but we should look into how this affects our models and model loading.
• Switch from typing.Union to PEP 604 union annotations with |
  • These were added in 3.10 and (in my opinion) are more readable and reduce friction for type-annotating code.
• Bump some dependency versions
• Update CI to test newer python versions