The auto-flush that runs when reconnecting (or turning Offline Mode
back off) only ever tried once — any operation that still failed on
that attempt sat stuck until the user manually hit Retry or
connectivity changed again. Now retries every 5 minutes for as long as
anything's still pending and the signal stays on, stopping on its own
once the queue is empty. Full Local Sync's existing 20-minute loop is
unaffected/separate.