fix: add staleTime to prevent excessive refetching

useInitializeLearnerHome() is consumed by 15+ components, and with
staleTime defaulting to 0, every mount and window focus triggered a
redundant background refetch. Set staleTime to 5 minutes since
dashboard data rarely changes while the user is viewing it.

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

Author: arbrandes

src/data/hooks/queryHooks.ts

@@ -15,6 +15,7 @@ const useInitializeLearnerHome = () => {
   const query = useQuery({
     queryKey: learnerDashboardQueryKeys.initialize(masqueradeUser),
     queryFn: async () => initializeList(masqueradeUser),
+    staleTime: 5 * 60 * 1000, // 5 minutes — dashboard data rarely changes while viewing
     retry: false,
     retryOnMount: !masqueradeUser,
     refetchOnMount: !masqueradeUser,