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/app.config.ts

@@ -1,4 +1,9 @@
-import { ApplicationConfig, LOCALE_ID, isDevMode, provideBrowserGlobalErrorListeners } from '@angular/core';
+import {
+  ApplicationConfig,
+  LOCALE_ID,
+  isDevMode,
+  provideBrowserGlobalErrorListeners,
+} from '@angular/core';
 import { provideRouter, withViewTransitions } from '@angular/router';
 import type { ActivatedRouteSnapshot } from '@angular/router';
 import { provideHttpClient, withInterceptors } from '@angular/common/http';
@@ -43,5 +48,5 @@ export const appConfig: ApplicationConfig = {
     provideApiClient(),
     { provide: SESSION_PORT, useExisting: SessionStore },
     { provide: LOCALE_ID, useValue: 'nl' },
-  ]
+  ],
 };