Pedagogy: add References / 참고문헌 entries to restructured chapters (Nakakuki + utokyo-ipp)

## Goal

Add explicit `References / 참고문헌` entries to the new chapters being created under the #402 restructure plan, plus existing notebooks that lack them. nmisp already cites international authors in mechanics/linux chapters (Pytel et al., William Shotts) — extend the same pattern to the Python-content chapters.

## Two distinct sources, different scopes

These are different categories of source and should be cited at different "weights." Don't conflate them.

### 1. Nakakuki Kenji — *Python for Engineers* (book) — broad scope

- **Korean edition** (the one read by the course author): 나카쿠키 켄지, 심효섭 역, *엔지니어를 위한 파이썬*, 제이펍, 2017. ISBN 979-11-88621-02-6. ([source repo](https://github.com/Jpub/scTechPython))
- **Original Japanese**: 中久喜 健司, *科学技術計算のためのPython入門 ――開発基礎、必須ライブラリ、高速化*, 技術評論社, 2016. ISBN 978-4-7741-8388-2. ([source repo](https://github.com/pyjbooks/py4science))

**Role**: architectural reference for the Python toolbox content (numpy, scipy, matplotlib, pandas) covered across `03_python_basics/` and `06_python_advanced/`. This is a textbook-weight citation, comparable to Pytel et al. for the mechanics chapters.

### 2. utokyo-ipp.github.io — narrow scope

- University of Tokyo, *Pythonプログラミング入門*, (CC BY-NC-ND 4.0).

**Role**: structural influence on **the testing/debugging chapter (#392) only**. Not a textbook-weight citation; just a "this idea was shaped partly by this public curriculum" link in the chapter's Further reading cell. **Do not** list in the README — that would over-weight a single-chapter influence.

## Where to add

- [ ] **README** — add a `## References / 참고문헌` section listing the **Nakakuki book** alongside existing references (Pytel et al., Shotts). utokyo-ipp does **not** belong here.
- [ ] **`06_python_advanced/10_testing_debugging.ipynb`** (#392) — `## Further reading` cell at the end with the utokyo-ipp link, framed as a structural influence on the chapter.
- [ ] **First notebook of `03_python_basics/`** (per #391) — Reference cell citing Nakakuki as the Python-content architectural source.
- [ ] **First notebook of `06_python_advanced/`** — same Nakakuki citation.

## Format

Match the bilingual pattern already used in `30_num_int/30_T_section_centroid.ipynb` and `60_linear_algebra_2/110_Beam_Reaction_Force.ipynb`:

```
참고문헌 : 저자, 제목, 출판사, 연도.
Ref: Author, Title, Publisher, Year.
```

For Nakakuki, cite the Korean translation primarily (the read edition) with the Japanese original in parentheses or on a second line.

## Why

- Fair credit signals scholarship and is a virtue of open-source educational material.
- The #402 restructure reshapes the Python content significantly; tracking which references shaped which chapter helps future contributors and translators stay aligned.
- Distinguishing scope (textbook vs. one-chapter influence) keeps the citations honest.

## Acceptance

- [ ] README has a `## References / 참고문헌` section listing Nakakuki + existing references.
- [ ] #392 notebook ends with a Further reading cell that includes the utokyo-ipp link.
- [ ] First notebooks of `03_python_basics/` and `06_python_advanced/` each cite Nakakuki.
- [ ] All new citations are bilingual (Korean + romanized/English where appropriate).
- [ ] utokyo-ipp does **not** appear in the README.

## Dependency

- Notebook-level citations need their host notebooks to exist first (per #391, #392, etc.). README citation can land independently any time.