fix: Handle new projects API response format in Sidebar

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

frontend/src/components/Sidebar.jsx

@@ -21,7 +21,7 @@ export function Sidebar({
   useEffect(() => {
     fetch(`${API_URL}/api/projects`)
       .then(res => res.json())
-      .then(setProjects)
+      .then(data => setProjects(data.projects || data))
       .catch(console.error);
   }, []);