docs: ✍️ Scribe: Add make docs troubleshooting to README

[fderuiter]

💡 What: Added troubleshooting for make docs failing with Command not found: sphinx-apidoc to README.md and added a journal entry.
🎯 Why: To resolve a recurring missing dependency error when new developers try to build documentation.
🧠 Cognitive Impact: Prevents frustration and clarifies that documentation dependencies require an extra install flag (--all-extras).
📖 Preview:

**Command not found: sphinx-apidoc when running make docs**
If building documentation with `make docs` fails with `Command not found: sphinx-apidoc`, run `poetry install --all-extras` first to install all necessary documentation plugins and dependencies.

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PR created automatically by Jules for task 11160830870897397588 started by @fderuiter

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