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/nodered/start.sh

@@ -0,0 +1,14 @@
+#!/bin/sh
+echo "[start.sh] BEGIN"
+INDEX=/data/node_modules/@flowfuse/node-red-dashboard/dist/index.html
+BASE_HREF="${DASHBOARD_BASE_HREF:-/dashboard/}"
+echo "[start.sh] INDEX=$INDEX BASE_HREF=$BASE_HREF"
+echo "[start.sh] has_base_before=$(grep -c '<base href' $INDEX 2>&1 || echo none)"
+if [ -f "$INDEX" ] && ! grep -q '<base href' "$INDEX"; then
+    sed -i "s|<meta name=\"description\"|<base href=\"$BASE_HREF\">
+    <meta name=\"description\"|" "$INDEX"
+    echo "[start.sh] PATCHED"
+fi
+echo "[start.sh] has_base_after=$(grep -c '<base href' $INDEX 2>&1 || echo none)"
+cd /usr/src/node-red
+exec node $NODE_OPTIONS node_modules/node-red/red.js $FLOWS