[ENH] Adding `AptaDiff` algorithm to pyaptamer

[siddharth7113]

• Code
• Paper

[purvanshjoshi]

Hi @siddharth7113,

I'd love to help add AptaDiff to pyaptamer!

We can implement it under a new pyaptamer/aptadiff module, structuring the VAE, Multinomial Diffusion, and Bayesian Optimization components to match the library's skbase design patterns. I'll also modernize the neural network code to support Python >= 3.10 and PyTorch >= 2.12.0.