Startup sequence

1. Boot — MCUboot loads the application. On boards with a modem reset GPIO, modem_reset.c pulses the nRF91 reset line before the modules start. The nRF Cloud library logs the device ID (from the host HW ID), protocol, and security tag.
2. Network - The network module connects on startup. When L4 connectivity is established it publishes NETWORK_CONNECTED.
3. Cloud - On network up, the cloud module waits for valid time (NTP over PPP) and installed credentials, then calls nrf_cloud_coap_connect(). Missing credentials or time cause a retry every 10 seconds (CONFIG_APP_CLOUD_CREDENTIAL_RETRY_SECONDS).
4. Main - When the cloud module publishes CLOUD_CONNECTED, main transitions to the cloud-connected state and runs the first cloud synchronization.