fix: starred routes not showing — starKey prefix mismatch

collectStarredItems used 'app:' prefix for route keys but
buildAppTreeNodes uses 'route:' prefix. Routes were starred
but never matched in the starred section.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/components/LayoutShell.tsx

@@ -167,7 +167,7 @@ function collectStarredItems(apps: SidebarApp[], starredIds: Set<string>): Starr
       items.push({ starKey: `app:${app.id}`, label: app.name, icon: makeStatusDot(app.health), path: `/apps/${app.id}` });
     }
     for (const route of app.routes) {
-      const key = `app:${app.id}/${route.id}`;
+      const key = `route:${app.id}/${route.id}`;
       if (starredIds.has(key)) {
         items.push({ starKey: key, label: route.name, path: `/apps/${app.id}/${route.id}`, parentApp: app.name });
       }