Root cause: backend filtered switches by status='online', so a mid-poll-cycle
device (briefly 'unknown') caused the endpoint to return [] — and the frontend
rendered nothing when the array was empty.
- Backend: query ALL switch devices (not just online ones); unreachable devices
already fall through to the Promise.allSettled error path and render with an
error badge, so no data is lost
- Frontend: replace silent `length > 0 &&` guard with a three-way ternary that
shows a "No managed switches found" message when the array is empty, so the
user always sees feedback instead of a blank section
- Frontend: add staleTime: 60_000 to the SNMP query to prevent the hair-trigger
background refetch that raced with the poller on every navigation
2GT-Rich
3eb85087f2