v4.0.2

• Bug fix: charges restored for charge-predicting potentials (QET) in the ASE calculators.
  PESCalculator.get_charges() raised PropertyNotImplementedError because the PyG calculator never
  implemented the charge output of the removed DGL calculator, and total_charge was silently ignored:
  charged cells ran as neutral (QEq treats a missing total charge as 0) with no error. PESCalculator
  now exposes "charges" in results and accepts total_charge / ext_pot kwargs, falling back to
  atoms.get_initial_charges(). Relaxer and MolecularDynamics inherit this. JAXPESCalculator
  gains the same support; make_potential_fn(with_charges=True) (QET only) returns
  (E, forces, stress, charges) with total_charge as a traced argument, so varying it triggers no
  recompilation. If you ran charged-cell MD or relaxations with QET on 4.0.0/4.0.1, those runs used
  a neutral cell.
• Bug fix: state_attr is cast to long before the nn.Embedding lookup in EmbeddingBlock,
  fixing failures with float state attributes.
• Internal: the electrostatics modules (LinearQeq, electrostatic potential) now live in
  matgl.layers; no public API change. Backend-related redirects removed. Notebooks updated to
  remove DGL references.