Paul Payne
6c00a9d33c
feat(mesh): NATS JetStream transport replacing MQTT
Replace the Mosquitto/paho mesh transport with NATS JetStream KV:
- mesh_wire.py: transport-agnostic registry (de)serialization (secret-stripped)
- nats_client.py: async CastleNATSClient — registry in the castle-registry KV
bucket, heartbeat liveness, delete-on-stop offline, watch-driven mesh state
- rewire main/config/models/nodes; MeshStatus -> connected/nats_url
- frontend MeshStatus + MeshPanel to the new fields
- drop paho-mqtt/mqtt_client + _mqtt._tcp mDNS browse; add nats-py
- keep the secret-stripping invariant; mDNS peer discovery retained
Single-node verified; two-node parity pending the second node.