Migrate to PyTorch (sleap-nn)

[gitttt-1234]

Description

This PR updates core components to migrate to PyTorch (SLEAP-NN), removing TensorFlow dependencies.

Types of changes

• [ ] Bugfix
• [x] New feature
• [x] Refactor / Code style update (no logical changes)
• [ ] Build / CI changes
• [ ] Documentation Update
• [ ] Other (explain)

Does this address any currently open issues?

#2159

Outside contributors checklist

• [ ] Review the guidelines for contributing to this repository
• [ ] Read and sign the CLA and add yourself to the authors list
• [ ] Make sure you are making a pull request against the develop branch (not main). Also you should start your branch off develop
• [ ] Add tests that prove your fix is effective or that your feature works
• [ ] Add necessary documentation (if appropriate)

Thank you for contributing to SLEAP!

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