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>

src/app/shared/infrastructure/scenario.interceptor.ts

@@ -21,8 +21,11 @@ export const scenarioInterceptor: HttpInterceptorFn = (req, next) => {
       return of(new HttpResponse({ status: 200, body: '[]' })).pipe(delay(400));
     case 'error':
       return timer(400).pipe(
-        switchMap(() => throwError(() =>
-          new HttpErrorResponse({ status: 500, statusText: 'Demo-fout', url: req.url }))),
+        switchMap(() =>
+          throwError(
+            () => new HttpErrorResponse({ status: 500, statusText: 'Demo-fout', url: req.url }),
+          ),
+        ),
       );
     default:
       return next(req);