fix: QA audit — lint cleanup, i18n fixes, module visibility, sidebar UX

- Fix 97 lint errors → 0 (unused imports, params, variables across 40+ files)
- Fix i18n key format: colon → dot notation for next-intl compatibility
- Add missing i18n keys (routes.application, routes.home, confirm)
- Fix module visibility: sidebar now respects per-account DB features
- Fix inject function: use dot-notation keys, add collapsed:true defaults
- Fix ConfirmDialog: use useTranslations instead of hardcoded German defaults
- Fix events page: replace placeholder 'Beschreibung' with proper description
- Fix Dockerfile: add NEXT_PUBLIC_CI ARG for Docker builds
- Collapse secondary sidebar sections by default for cleaner UX

apps/web/app/layout.tsx

@@ -4,5 +4,5 @@ import { Noto_Serif } from 'next/font/google';
 const notoSerif = Noto_Serif({ subsets: ['latin'], variable: '--font-serif' });
 
 export default function RootLayout({ children }: React.PropsWithChildren) {
-  return children;
+  return <div className={notoSerif.variable}>{children}</div>;
 }