When a node was already known (via link-node) but had an empty onion
address, the peer-joined handler returned early without updating the
onion. Now it patches missing onion/pubkey fields on existing nodes.
Also adds update_node() to federation storage and updates the
architecture comparison doc with system resources, StartOS/umbrelOS
tabs, Web5 section, and comparison view.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>