chore(docs): remove the unused Common Use Cases page

[helmihyo]

Matti's call in #34: "Just remove the use-cases.md page altogether. It's not used; no need to carry it around."

What it was

A seven-line stub — a bulleted list of five topics somebody intended to write:

# Common Use Cases

- Marine navigation system setup
- Data logging and monitoring
- Signal K server configuration
- Integration with existing boat systems
- Industrial automation applications

Stub pages are normal here; CLAUDE.md says so, and eight others are equally short. What made this one different is that it was the only stub missing from nav, so nothing linked to it and it could only be reached by typing the URL. It nonetheless existed in all ten languages, which meant nine translations of a list of headings.

Verified before removing

References in mkdocs.yml	0
Links from any page	0
Files removed	10 (English plus nine translations)

Verified after

mkdocs build --strict	clean
check_anchors.py	all anchors resolve
translation_status.py	20 pages per language, orphaned=0 in all nine

orphaned=0 matters: the status script flags a translation whose English source has gone, so a partial deletion would have shown up here.

One consequence worth stating

https://docs.hatlabs.fi/halpi2/user-guide/use-cases/ currently returns 200 and will 404 after this merges. Nothing on the site linked there, so the only way to reach it is an old bookmark.

#34 stays open

This addresses only the third item. The French and German terminology drift — coupure de courant prescribed but perte d'alimentation used, and German carrying both Spannungsausfall and Stromausfall — is untouched.

🤖 Generated with Claude Code

[github-actions]

Translation status

da — 20 current
de — 20 current
es — 20 current
fi — 20 current
fr — 20 current
it — 20 current
nb — 20 current
nl — 20 current
sv — 20 current

Every translation of the pages in scope is current.