Firmware sends node_id=1 for all nodes (relates to #232)

[shy-workstation]

Despite NVS provisioning each node with a different node_id (1-4), all UDP packets contain node_id=1 at byte offset 4.
Boot log confirms NVS reads correctly:

nvs_config: NVS override: node_id=4
main: ESP32-S3 CSI Node (ADR-018) — Node ID: 4
csi_collector: CSI collection initialized (node_id=1, channel=11)

NVS loads node_id=4 but csi_collector still uses 1. Same issue as #232.

Workaround: The relay script patches byte 4 based on source IP address.