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feat: implement O1NumHess for efficient numerical Hessian calculation

- Add O(1) Numerical Hessian (O1NumHess) implementation in `o1numhess.py`.
- Utilize Off-Diagonal Low-Rank (ODLR) approximation and random projection techniques.
- Reduce computational scaling from O(N) to approximately O(1) for large-scale systems.

Author: ss0832