Add infra/ — full stack config as deployed on RPi 3B+

Captures everything needed to rebuild the stack from scratch:

infra/compose.yaml
- mosquitto (eclipse-mosquitto:latest)
- zigbee2mqtt (ghcr.io/pine64/zigbee2mqtt:latest-dev, BLZ fork)
- nodered (nodered/node-red:latest)

infra/mosquitto/config/mosquitto.conf
- anonymous listener on 1883, file logging, persistence on

infra/zigbee2mqtt/
- configuration.yaml: 5 paired devices with friendly names, 1 group
- coordinator_backup.json: zigbee network key + pan id (recovery)
- state.json: per-device persisted state (ON/OFF, linkquality)

infra/nodered/
- settings.js: nodered defaults (flowFile: flows.json, no auth)
- start.sh: patches Dashboard 2.0 SPA with <base href> at startup

Also:
- Updated z2m groups section to rename Laser & Fog -> DJ Booth
  (matches the friendly_name already in devices section)
- Pushed the same change to live /root/zigbee2mqtt/configuration.yaml
  and restarted the zigbee2mqtt container
- .gitignore: output/ (regenerated on every build, churns uuid ids)
- README.md: link to infra/README.md for rebuild procedure

infra/README.md

@@ -0,0 +1,36 @@
+# infra/
+
+Full stack configuration as deployed on the RPi 3B+ at `192.168.81.147`.
+
+## Layout on host
+
+```
+/root/
+├── compose.yaml                       → infra/compose.yaml
+├── mosquitto/config/mosquitto.conf    → infra/mosquitto/config/mosquitto.conf
+├── zigbee2mqtt/                       → infra/zigbee2mqtt/
+│   ├── configuration.yaml             # device pairings + friendly names + groups
+│   ├── coordinator_backup.json        # zigbee network key + pan id (recovery)
+│   └── state.json                     # per-device persisted state (ON/OFF, etc.)
+└── nodered/                           → bind-mount for nodered container's /data
+    ├── flows.json                     → generated from ../flows/zigbee-monitor.yaml
+    ├── settings.js                    → infra/nodered/settings.js
+    └── start.sh                       → infra/nodered/start.sh (patches Dashboard SPA)
+```
+
+## Rebuild procedure from a fresh host
+
+1. Install Docker, `docker compose`.
+2. Clone this repo, `cd infra`.
+3. `mkdir -p mosquitto/data mosquitto/log` (empty dirs for the volume mounts).
+4. `docker compose up -d`.
+5. Pair zigbee devices (IEEE addresses in `zigbee2mqtt/configuration.yaml` will be wrong; re-pair or use the existing `coordinator_backup.json` to rejoin the same network).
+6. `just deploy` from the repo root to push the Node-RED flow.
+
+## Files that drift at runtime
+
+- `nodered/flows.json` — managed by the generator, do not hand-edit.
+- `nodered/node_modules/@flowfuse/node-red-dashboard/dist/index.html` — patched by `start.sh` at every container start; survives reboots, lost on `docker compose down -v`.
+- `mosquitto/data/` — broker persistence, transient.
+- `zigbee2mqtt/database.db` — sqlite, transient (regenerated from `configuration.yaml` + `coordinator_backup.json`).
+- `zigbee2mqtt/state.json` — committed so device ON/OFF state survives full rebuilds.