The data.dir field is what should be on the persistent volume. Try changing your fly.toml mount to:
[mounts]
source="app_data"
destination="/var/lib/litefs"
The data directory is being wiped out when you restart your machine which also clears out the cluster ID so that’s why it autogenerates a new one and can’t connect to Consul.
We’re working on improving the setup for LiteFS so it’s not quite as complicated.