- Emit ISO-8601 timestamps and string level labels (info/warn/...) so
Portainer's log viewer renders seconds and human-readable levels.
- Classify ETIMEDOUT/ECONNRESET/EPIPE/ENOTCONN as info one-liners
rather than warns with stack traces. These are routine on cellular.
- Add an info "frame ingested" line per accepted AVL frame so device
activity is visible at info level until task 1.10 wires up prom-client.