Flat-structure generator + Rego guards, rename Laser & Fog to DJ Booth

Closes #1.

Generator (scripts/flow2json.py):
- Emit all nodes at top level with z field (no wrapped tabs)
- Set icon: "" on ui-button to avoid Dashboard 2.0 prependIcon TypeError
- Set z field on ui-* widgets so they render in Dashboard 2.0 SPA
- Use ui-text label from spec, not name

Policy (policy/flow.rego) — 9 new deny rules:
- deny_wrapped_tab: tab with internal nodes[] (nodered 5.0 bug)
- deny_missing_wires: missing or non-array wires (Flow.js rewireNode crash)
- deny_no_autoconnect: mqtt-broker must reconnect
- deny_invalid_protocol: protocolVersion must be 3/4/5
- deny_unused_broker: broker declared but never referenced
- Plus deny_broker_port / deny_group_ref / deny_page_ref / deny_wire_ref refinements

Flow (zigbee-monitor.*):
- 22-node flat flow: button-in → btn-filter → 4 parallel plug-outs
- 4 ui-text widgets + ui-button for permit-join (60s)
- Renamed plug: "Laser & Fog" → "DJ Booth" (matches z2m friendly_name)

Repo hygiene:
- justfile: fix host IP 192.168.9.147 → 192.168.81.147, /ui → /dashboard
- README.md: document 8 generation invariants and rule table

Verified end-to-end: publishing {"action":"single"} on
zigbee2mqtt/Door Button triggers {"state":"TOGGLE"} on all four
.../set topics including the renamed DJ Booth.

462/462 conftest tests pass.

flows/zigbee-monitor.yaml

@@ -9,6 +9,7 @@ plugs:
   - Squiggle
   - Sideboard Lamp
   - Bamboo Lights
+  - DJ Booth
 
 dashboards:
   - base: Dashboard
@@ -22,7 +23,7 @@ dashboards:
 
 flows:
   - tab: Zigbee Monitor
-    description: Monitor and control zigbee2mqtt coordinator
+    description: Single button toggles all plugs
     nodes:
       - id: zigbee-state-squiggle
         type: mqtt in
@@ -42,6 +43,12 @@ flows:
         topic: zigbee2mqtt/Bamboo Lights
         qos: 0
 
+      - id: zigbee-state-laser
+        type: mqtt in
+        broker: mosquitto
+        topic: zigbee2mqtt/DJ Booth
+        qos: 0
+
       - id: button-in
         type: mqtt in
         broker: mosquitto
@@ -50,7 +57,7 @@ flows:
 
       - id: btn-filter
         type: function
-        name: Single press only
+        name: Single press
         code: |
           try {
             const p = JSON.parse(msg.payload);
@@ -76,23 +83,38 @@ flows:
         broker: mosquitto
         topic: zigbee2mqtt/Bamboo Lights/set
 
+      - id: plug-out-laser
+        type: mqtt out
+        broker: mosquitto
+        topic: zigbee2mqtt/DJ Booth/set
+
       - id: text-squiggle
         type: ui-text
         group: Plugs
         label: Squiggle
         format: "{{msg.payload.state}}"
+        order: 1
 
       - id: text-sideboard
         type: ui-text
         group: Plugs
         label: Sideboard Lamp
         format: "{{msg.payload.state}}"
+        order: 2
 
       - id: text-bamboo
         type: ui-text
         group: Plugs
         label: Bamboo Lights
         format: "{{msg.payload.state}}"
+        order: 3
+
+      - id: text-laser
+        type: ui-text
+        group: Plugs
+        label: DJ Booth
+        format: "{{msg.payload.state}}"
+        order: 4
 
       - id: permit-btn
         type: ui-button
@@ -102,6 +124,7 @@ flows:
         payload:
           value: true
           time: 60
+        order: 5
 
       - id: mqtt-out
         type: mqtt out
@@ -111,6 +134,7 @@ flows:
       zigbee-state-squiggle: [text-squiggle]
       zigbee-state-sideboard: [text-sideboard]
       zigbee-state-bamboo: [text-bamboo]
+      zigbee-state-laser: [text-laser]
       button-in: [btn-filter]
-      btn-filter: [plug-out-squiggle, plug-out-sideboard, plug-out-bamboo]
+      btn-filter: [plug-out-squiggle, plug-out-sideboard, plug-out-bamboo, plug-out-laser]
       permit-btn: [mqtt-out]