fix: move useMemo before early return for hooks rules

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: nolancacheux

src/components/3d/NetworkVisualization.tsx

@@ -322,9 +322,7 @@ function GridFloor() {
 function BackgroundStars() {
   const theme = useNetworkStore(state => state.ui.theme);
 
-  if (theme !== 'dark') return null;
-
-  // Use useMemo to generate consistent star positions
+  // Use useMemo to generate consistent star positions (must be called before any early returns)
   const stars = useMemo(() => {
     return Array.from({ length: 100 }).map((_, i) => ({
       position: [
@@ -337,6 +335,8 @@ function BackgroundStars() {
     }));
   }, []);
 
+  if (theme !== 'dark') return null;
+
   return (
     <>
       {stars.map((star, i) => (