Fix state.to() not propagating dtype/device to constraints & expose angle_tolerance in symmetry pipeline

[danielzuegner]

Summary

1. state.to(dtype=...) did not update constraint tensors.
   _state_to_device only converted top-level SimState tensor attributes (positions, cell, masses) but left constraint objects untouched. This meant internal tensors like FixSymmetry.rotations or FixCom.coms stayed on the original dtype/device, causing silent dtype mismatches.
2. state.to(dtype=...) did not update sub-class tensor attributes like forces, velocities, ....
3. angle_tolerance could not be passed to moyopy for symmetry detection.
   MoyoDataset supports an angle_tolerance parameter, but it wasn't exposed anywhere in the TorchSim symmetry pipeline.

Changes

Constraint dtype/device propagation

torch_sim/constraints.py, torch_sim/state.py

• Added Constraint.to(device, dtype) as a base no-op, with concrete overrides on each subclass:

  Class	What to() moves
  AtomConstraint	atom_idx
  SystemConstraint	system_idx
  FixCom	system_idx + cached coms tensor
  FixSymmetry	rotations (float→dtype), symm_maps (int→device only), reference_cells

• Each to() follows the same explicit-constructor pattern used by reindex, merge, and select_constraint.
• _state_to_device now calls .to() on each attached constraint.

_state_to_device dtype handling

torch_sim/state.py

• The main tensor loop now applies both device and dtype: all floating-point tensors get .to(device=device, dtype=dtype), integer/bool tensors get .to(device=device) only.
• This replaces the previous approach of hardcoding positions/masses/cell for dtype conversion, so subclass attributes like forces and momenta are now handled automatically.

Expose angle_tolerance

torch_sim/symmetrize.py, torch_sim/constraints.py

• Added angle_tolerance: float | None = None parameter to:
  • _moyo_dataset
  • get_symmetry_datasets
  • prep_symmetry
  • _refine_symmetry_impl
  • refine_symmetry
  • refine_and_prep_symmetry
• Threaded through FixSymmetry.from_state().
• Passed to MoyoDataset(…, angle_tolerance=angle_tolerance).

Checklist

Before a pull request can be merged, the following items must be checked:

• Doc strings have been added in the Google docstring format.
• Run ruff on your code.
• Tests have been added for any new functionality or bug fixes.

[CompRhys]

just the linting and then good to merge?

[danielzuegner]

Hopefully good to go -- I've fixed the last remaining linting error that was introduced by this PR. The others are pre-existing I believe.