fix: server-side render InitialLoader via cookies to prevent FOUC and add video preload

Former-commit-id: 2af58c1fa51fbe807132e879995ffe75ec59b7b6

components/providers/InitialLoader.tsx

@@ -7,20 +7,12 @@ const PRELOAD_VIDEOS = [
   '/assets/videos/web/hero-bohrung.mp4'
 ];
 
-export function InitialLoader() {
-  const [isLoading, setIsLoading] = useState(true);
-  const [isClient, setIsClient] = useState(false);
+export function InitialLoader({ shouldShowLoader = true }: { shouldShowLoader?: boolean }) {
+  const [isLoading, setIsLoading] = useState(shouldShowLoader);
 
   useEffect(() => {
-    setIsClient(true);
+    if (!shouldShowLoader) return;
     
-    // Prüfen, ob wir in dieser Session schon geladen haben
-    const hasLoaded = sessionStorage.getItem('etib_initial_load');
-    if (hasLoaded) {
-      setIsLoading(false);
-      return;
-    }
-
     // Fallback Timeout (4 Sekunden), falls Videos hängen
     const timeout = setTimeout(() => {
       finishLoading();
@@ -48,15 +40,16 @@ export function InitialLoader() {
 
     // Cleanup
     return () => clearTimeout(timeout);
-  }, []);
+  }, [shouldShowLoader]);
 
   const finishLoading = () => {
-    sessionStorage.setItem('etib_initial_load', 'true');
+    // Set a session cookie so the server knows not to render the loader again
+    document.cookie = "etib_initial_load=true; path=/; samesite=lax";
     setIsLoading(false);
   };
 
-  // Wir rendern serverseitig nichts blockierendes (Hydration Mismatch verhindern)
-  if (!isClient) return null;
+  // Wenn wir serverseitig rendern und es nicht zeigen sollen, return null
+  if (!shouldShowLoader) return null;
 
   return (
     <AnimatePresence>