Analysis: Noise Floor Delta over Z-axis

[AhmetCanSolak]

This PR introduces a way to quantify changes on noise profile spectrum between a denoised array and a noisy array. With current related work we do we need over Z-axis implementation at first but eventually axis can be an optional argument.

[royerloic]

Closing — Incomplete implementation

Thank you @AhmetCanSolak — the noise floor delta analysis concept is interesting but this PR has unresolved issues:

1. halfbit_curve() raises NotImplementedError — The core dependency is unimplemented
2. Demo has undefined variable — denoised_image is used but never defined in demo_noise_floor_delta()
3. Function signature mismatch — noise_floor_delta() takes 3 params but docstring describes 2

The concept of spectral noise floor analysis is documented for future implementation in code_review_reports/pr_ideas_for_future_work.md with the code and design intent preserved.