The node registry: one table that does discovery, dedup, and security

One structure, three responsibilities

The registry is the heart of the gateway. It tracks every known node and does three jobs at once:

1. Discovery — a broadcast beacon lets new nodes announce themselves; the registry records them as pending.
2. De-duplication & replay defense — each node's last-seen counter gates every incoming frame.
3. Liveness — a last-seen timestamp drives the "online / offline" state you see in the app and on the display.

Keeping it bounded

Embedded memory is finite and predictable behavior matters more than capacity. The registry is a fixed-size table sized for a real home or small industrial deployment. When it's full, admission is refused loudly rather than silently overwriting a node.

Bounded, inspectable, and easy to reason about beats clever and unbounded every time on a device that has to run for years without a reboot.