feat: upgrade UI with premium industrial aesthetics, purely visual language switch, and resilient error pages

Former-commit-id: e4d801c24e64c41816f86de9767b47894abb6806

components/providers/TransitionProvider.tsx

@@ -5,16 +5,18 @@ import { useRouter } from 'next/navigation';
 
 interface TransitionContextType {
   isTransitioning: boolean;
-  startTransition: (href: string) => void;
+  transitionMessage: string | null;
+  startTransition: (href: string, message?: string | null) => void;
 }
 
 const TransitionContext = createContext<TransitionContextType | undefined>(undefined);
 
 export function TransitionProvider({ children }: { children: ReactNode }) {
   const [isTransitioning, setIsTransitioning] = useState(false);
+  const [transitionMessage, setTransitionMessage] = useState<string | null>(null);
   const router = useRouter();
 
-  const startTransition = useCallback((href: string) => {
+  const startTransition = useCallback((href: string, message: string | null = null) => {
     // Wenn wir bereits navigieren, nichts tun
     if (isTransitioning) return;
     
@@ -25,6 +27,7 @@ export function TransitionProvider({ children }: { children: ReactNode }) {
        return;
     }
 
+    setTransitionMessage(message);
     setIsTransitioning(true);
 
     // Die Animation des Shutters abwarten (ca. 700ms), dann pushen
@@ -35,12 +38,14 @@ export function TransitionProvider({ children }: { children: ReactNode }) {
       // Next.js Route-Changes sind fast sofort da, aber wir geben dem Cache kurz Zeit
       setTimeout(() => {
         setIsTransitioning(false);
+        // Message etwas verzögert zurücksetzen, damit es während dem Ausblenden nicht verschwindet
+        setTimeout(() => setTransitionMessage(null), 300);
       }, 300);
     }, 700);
   }, [isTransitioning, router]);
 
   return (
-    <TransitionContext.Provider value={{ isTransitioning, startTransition }}>
+    <TransitionContext.Provider value={{ isTransitioning, transitionMessage, startTransition }}>
       {children}
     </TransitionContext.Provider>
   );