Add guarded GPU support for geometry engines

[NCCU-Schultz-Lab]

Summary

• Repair PySCF GPU offload during ASE geometry optimization by applying the migration path on every SCF/force evaluation.
• Record GPU device provenance in optimization and engine results.
• Add independently guarded PyFock GPU support through CuPy.
• Add engine-specific GPU diagnostics, optional CUDA extras, UI capability handling, CPU fallback, documentation, and regression tests.
• Add opt-in real-hardware validation gates for PySCF geometry optimization and PyFock GPU execution.

Validation

• Focused GPU, PyFock, CLI, worker-payload, and diagnostics tests pass.
• Black and Ruff checks pass.
• Real NVIDIA checks are opt-in and require a CUDA-capable host.
• PyFock GPU geometry optimization uses numerical forces because the current PyFock analytical gradient path is CPU-only.