feat(app-store): sort grid by stars and rotate featured weekly (#787)

Grid templates are now sorted by star count (descending) so popular
apps surface naturally rather than appearing in registry fetch order.

Featured hero rotates weekly among the top 5 starred apps instead of
always pinning the single highest-starred entry. Rotation is seeded
by week number so all nodes show the same featured app throughout a
given week. Registries with no star data gracefully skip the featured
hero and preserve their natural ordering.

frontend/src/components/AppStoreView.tsx

@@ -247,8 +247,10 @@ export function AppStoreView({ onDeploySuccess }: AppStoreViewProps) {
     }, [filtered, searchQuery]);
 
     const gridTemplates = useMemo(() => {
-        if (!featuredTemplate) return filtered;
-        return filtered.filter(t => t.title !== featuredTemplate.title);
+        const base = featuredTemplate
+            ? filtered.filter(t => t.title !== featuredTemplate.title)
+            : filtered;
+        return [...base].sort((a, b) => (b.stars ?? 0) - (a.stars ?? 0));
     }, [filtered, featuredTemplate]);
 
     return (