style: format frontend, docs and skills with prettier; add .prettierignore

One-time prettier --write so the new format:check CI gate starts green.
.prettierignore excludes generated (api-client.ts, documentation.json),
vendored (public/cibg-huisstijl), and backend (dotnet format owns it).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.claude/skills/new-feature/SKILL.md

@@ -33,6 +33,7 @@ Every feature is built inward-out. Never start with the component.
 ## Worked example
 
 The intake wizard slice, end to end:
+
 - `src/app/herregistratie/domain/intake.machine.ts` (+ spec)
 - `src/app/herregistratie/infrastructure/`
 - `src/app/herregistratie/ui/` (wizard component + page)