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/zigbee2mqtt/coordinator_backup.json

@@ -0,0 +1,26 @@
+{
+  "metadata": {
+    "format": "zigpy/open-coordinator-backup",
+    "version": 1,
+    "source": "zigbee-herdsman@10.5.0",
+    "internal": {
+      "date": "2026-07-01T05:51:05.408Z"
+    }
+  },
+  "stack_specific": {},
+  "coordinator_ieee": "0000000000000000",
+  "pan_id": "1a62",
+  "extended_pan_id": "dddddddddddddddd",
+  "nwk_update_id": 0,
+  "security_level": 5,
+  "channel": 11,
+  "channel_mask": [
+    11
+  ],
+  "network_key": {
+    "key": "01030507090b0d0f00020406080a0c0d",
+    "sequence_number": 0,
+    "frame_counter": 57407
+  },
+  "devices": []
+}