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.

justfile

@@ -37,7 +37,7 @@ validate-all:
 # ---- Deployment ----
 
 # Deploy flow to Node-RED instance
-deploy FLOW="zigbee-monitor" HOST="http://192.168.9.147:1880": generate validate
+deploy FLOW="zigbee-monitor" HOST="http://192.168.81.147:1880": generate validate
     @echo "=== Deploying {{FLOW}} to {{HOST}} ==="
     curl -s -o /dev/null -w "HTTP %{http_code}" \
         -X POST {{HOST}}/flows \
@@ -47,7 +47,7 @@ deploy FLOW="zigbee-monitor" HOST="http://192.168.9.147:1880": generate validate
     @echo ""
 
 # Quick deploy (skip validation)
-deploy-quick FLOW="zigbee-monitor" HOST="http://192.168.9.147:1880": generate
+deploy-quick FLOW="zigbee-monitor" HOST="http://192.168.81.147:1880": generate
     @echo "=== Quick deploy {{FLOW}} to {{HOST}} ==="
     curl -s -o /dev/null -w "HTTP %{http_code}" \
         -X POST {{HOST}}/flows \
@@ -59,12 +59,12 @@ deploy-quick FLOW="zigbee-monitor" HOST="http://192.168.9.147:1880": generate
 # ---- Viewing ----
 
 # Fetch and display current flows from Node-RED
-pull HOST="http://192.168.9.147:1880":
+pull HOST="http://192.168.81.147:1880":
     curl -s {{HOST}}/flows | python3 -m json.tool
 
 # Open dashboard in browser
 dashboard:
-    xdg-open http://192.168.9.147:1880/ui 2>/dev/null || open http://192.168.9.147:1880/ui 2>/dev/null || echo "Open: http://192.168.9.147:1880/ui"
+    xdg-open http://192.168.81.147:1880/dashboard 2>/dev/null || open http://192.168.81.147:1880/dashboard 2>/dev/null || echo "Open: http://192.168.81.147:1880/dashboard"
 
 # ---- Development ----