fix: remove unused refresh destructure from App.tsx after review fix

The prior review fix (#4) removed the redundant `await refresh()` call from
the onCreate handler, but left `refresh` in the useSessions() destructure.
TypeScript (noUnusedLocals) flagged it as an error, breaking the build.

Remove the unused binding to restore a clean build.

frontend/src/App.tsx

@@ -8,7 +8,7 @@ import { RightPanel } from './components/RightPanel'
 
 function App() {
   const { user, loading: authLoading, login, logout } = useAuth()
-  const { sessions, activeSessionId, createNew, switchTo, refresh } = useSessions()
+  const { sessions, activeSessionId, createNew, switchTo } = useSessions()
   const { messages, isStreaming, sendMessage } = useChat(activeSessionId)
 
   if (authLoading) {