Refactor: Optimize training loop and improve code style

* Standardize import order
* Fix errors in code comments
* Update docstrings to conform to reStructuredText (reST) style
* Replace ansatz block gate sequence with a single SU(4) gate
* Consolidate training functions for the three ansatzes
* Fix inefficient structure where Hamiltonian (H) was rebuilt every iteration
* H is now constructed only once per magnetic field strength

Author: QuiXamii