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>

README.md

@@ -74,6 +74,38 @@ Homelable continuously monitors your nodes and displays their live status (onlin
 
 ---
 
+## Zigbee2MQTT Import
+
+Homelable can connect directly to your MQTT broker and import your Zigbee network topology from **Zigbee2MQTT**, placing each device on the canvas as a typed node.
+
+### Prerequisites
+
+- A running **MQTT broker** (e.g. Mosquitto) accessible from the Homelable host
+- **Zigbee2MQTT** connected to the broker with at least one device paired
+
+### Usage
+
+1. Click **Zigbee Import** in the left sidebar (below "Scan Network")
+2. Enter your broker host, port (default `1883`), optional credentials, and base topic (default `zigbee2mqtt`)
+3. Click **Test Connection** to verify reachability, then **Fetch Devices**
+4. Select the devices you want from the grouped list (Coordinator / Router / End Device)
+5. Click **Add N to Canvas** — devices are placed in a grid with IoT edges
+
+### Node Types
+
+| Type | Z2M Device | Icon |
+|------|-----------|------|
+| `zigbee_coordinator` | Coordinator | Network hub |
+| `zigbee_router` | Router (mains-powered) | Radio |
+| `zigbee_enddevice` | End Device (battery) | Antenna |
+
+Hierarchy is set automatically: coordinator → routers → end devices (`parent_id`).
+LQI (Link Quality Indicator) is stored as a node property.
+
+> **Full documentation:** [docs/zigbee-import.md](./docs/zigbee-import.md)
+
+---
+
 ## Live View (read-only public canvas)
 
 Live View lets you share a read-only snapshot of your canvas with anyone on your network — no login required. It is disabled by default.