nodered: its MQTT broker comes from the mesh

Node-RED's one broker node pointed at zurag.be:1884, where nothing listens. nodered now requires
mqtt-topic (asking for every topic: flows follow the devices' own) and a run-once `mqtt` step —
declared last, restarted when the binding, credential or settings change — points the mesh's broker
nodes at the bound broker through Node-RED's admin API with the module's api-token: the node the
step makes itself when none is named, or the ones an assignment names in `mqtt.brokers`. Only host,
port, TLS and the login change; the broker is asked first whether it takes the login; the deploy is
against the revision read ("nodes", so only that node restarts) and a digest makes a rerun a no-op.
A broker node nobody named is never touched. settings.js keeps `mqtt` and `topics` out of Node-RED.

modules/nodered/package.json

@@ -1,9 +1,14 @@
 {
   "name": "@novox/module-nodered",
   "version": "0.1.0",
-  "description": "nodered — flow-based automation. Its client and tools live here (novox/hq ADR 0039).",
+  "description": "nodered \u2014 flow-based automation. Its client and tools live here (novox/hq ADR 0039).",
   "type": "module",
   "private": true,
+  "scripts": {
+    "build": "tsc client.ts tools/index.ts mqtt/probe.ts mqtt/connection.ts mqtt/index.ts --module NodeNext --moduleResolution NodeNext --target ES2022 --outDir dist",
+    "typecheck": "tsc -p tsconfig.json",
+    "test": "node --test --experimental-strip-types 'test/*.test.ts'"
+  },
   "dependencies": {
     "@novox/mesh-sdk": "^0.1.0"
   },