feat: Hintergrund-Animation 'Background Grey Wave' als Fullscreen-Layer

Lottie-Animation fixed hinter allen Inhalten, 100vw/100vh skaliert.
Header mit Glassmorphism-Effekt (backdrop-filter blur) damit Inhalt
beim Scrollen lesbar bleibt.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

style.css

@@ -9,8 +9,24 @@ body {
   min-height: 100vh;
 }
 
+#lottie-bg {
+  position: fixed;
+  inset: 0;
+  width: 100vw;
+  height: 100vh;
+  z-index: 0;
+  pointer-events: none;
+}
+
+#lottie-bg svg {
+  width: 100% !important;
+  height: 100% !important;
+}
+
 header {
-  background: #fff;
+  background: rgba(255,255,255,0.85);
+  backdrop-filter: blur(8px);
+  -webkit-backdrop-filter: blur(8px);
   border-bottom: 1px solid #ddd;
   padding: 1rem 1.5rem;
   position: sticky;
@@ -18,6 +34,11 @@ header {
   z-index: 10;
 }
 
+main {
+  position: relative;
+  z-index: 1;
+}
+
 header h1 { font-size: 3rem; margin-bottom: 0; }
 
 nav { display: flex; gap: 0.5rem; }