feat: add Zigbee2MQTT network map importer

- Backend: async MQTT service (aiomqtt) to fetch Z2M networkmap via bridge API
- Backend: FastAPI router at /api/v1/zigbee with /import and /test-connection
- Backend: Pydantic v2 schemas for request/response validation
- Backend: coordinator → router → end-device parent_id hierarchy builder
- Frontend: ZigbeeImportModal with MQTT config form, Test Connection, Fetch Devices
- Frontend: device list grouped by type (coordinator/router/enddevice) with checkboxes
- Frontend: ZigbeeCoordinatorNode, ZigbeeRouterNode, ZigbeeEndDeviceNode canvas nodes
- Frontend: Zigbee Import button in sidebar alongside Scan Network
- Frontend: handleZigbeeAddToCanvas wires selected devices + edges onto canvas
- Tests: full unit test suite for parser, hierarchy builder, MQTT mocks
- Tests: API endpoint tests for /zigbee/import and /zigbee/test-connection
- Tests: Vitest component tests for ZigbeeImportModal
- Docs: docs/zigbee-import.md with full usage, MQTT config, troubleshooting guide
- Docs: README.md Zigbee2MQTT Import section

Co-authored-by: CyberKeys <noreply@openclaw.ai>

frontend/src/components/canvas/nodes/index.tsx

@@ -1,7 +1,7 @@
 import { type NodeProps, type Node } from '@xyflow/react'
 import {
   Globe, Router, Network, Server, Layers, Box, Container,
-  HardDrive, Cpu, Wifi, Circle, Cctv, Printer, Monitor, PlugZap, Anchor, Package, Flame,
+  HardDrive, Cpu, Wifi, Circle, Cctv, Printer, Monitor, PlugZap, Anchor, Package, Flame, Radio, Antenna,
 } from 'lucide-react'
 import { BaseNode } from './BaseNode'
 import type { NodeData } from '@/types'
@@ -26,3 +26,7 @@ export const CplNode      = (props: N) => <BaseNode {...props} icon={PlugZap} />
 export const DockerHostNode      = (props: N) => <BaseNode {...props} icon={Anchor} />
 export const DockerContainerNode = (props: N) => <BaseNode {...props} icon={Package} />
 export const GenericNode  = (props: N) => <BaseNode {...props} icon={Circle} />
+// Zigbee node types
+export const ZigbeeCoordinatorNode = (props: N) => <BaseNode {...props} icon={Network} />
+export const ZigbeeRouterNode      = (props: N) => <BaseNode {...props} icon={Radio} />
+export const ZigbeeEndDeviceNode   = (props: N) => <BaseNode {...props} icon={Antenna} />