feat: Implement multi-node support with MQTT and mDNS for service discovery and coordination

TODO.md

@@ -3,8 +3,19 @@
 - Remove devbox-connect. Instead, make it easy to copy an ssh tunnel command to expose all ports of all services to a remote box: `ssh -L 9000:localhost:9000 payne@dev.payne.io, etc.
 - Add a scripts dir?
 
-- tools: use std-in/std-out unix philosophy
-- daemons or web-services: expose ports
-- workers: just keep doing work in a background--usually watching the filesystem or a queue
-- jobs: scheduled tools or daemon requests
-- frontend: files served up by caddy
+- Component (software units) types:
+  - python/golang/rust/bash tool: use std-in/std-out unix philosophy
+  - python/golang/rust-daemon: Whatever
+  - python web-service: RESTful, fastapi, SSE, etc.
+  - react-frontend
+  - python API
+
+- Dependencies
+  - docker/podman (mqtt)
+  - all component system dependencies
+  - uv
+  - golang/rust/java/.net/whatever
+
+- Add amplifier to make a component builder
+
+-  What's this about? "I need to add the MQTT env vars to the systemd unit. Let me add them via a drop-in override so the deploy command doesn't overwrite them."