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>

.storybook/preview.ts

@@ -11,9 +11,7 @@ if (typeof document !== 'undefined') document.body.classList.add('brand--cibg');
 const preview: Preview = {
   // CIBG/Bootstrap styles bare elements — no theme wrapper class needed; just pad.
   // The token bridge lives in styles.scss (loaded via the app build target).
-  decorators: [
-    componentWrapperDecorator((story) => `<div style="padding:1.5rem">${story}</div>`),
-  ],
+  decorators: [componentWrapperDecorator((story) => `<div style="padding:1.5rem">${story}</div>`)],
   parameters: {
     layout: 'padded',
     // Accessibility (axe) via @storybook/addon-a11y. Runs WCAG 2.0/2.1 A+AA rule