feat: add Z-Wave network scan via MQTT gateway

Import a Z-Wave JS UI (zwavejs2mqtt) network over the MQTT gateway API,
mirroring the existing Zigbee pipeline:

- New Z-Wave Import modal + sidebar entry (broker, prefix, gateway name)
- coordinator/router/end-device typing with mesh tree from node neighbors
- import to Pending section or straight to canvas
- Pending Devices gains a Z-Wave source filter
- shared mqtt_common helpers extracted from the zigbee service

ha-relevant: yes

frontend/src/utils/zwaveProperties.ts

@@ -0,0 +1,21 @@
+import type { NodeProperty, NodeType } from '@/types'
+
+const ZWAVE_TYPES: NodeType[] = ['zwave_coordinator', 'zwave_router', 'zwave_enddevice']
+
+export function isZwaveType(type: NodeType | string | undefined | null): boolean {
+  return !!type && (ZWAVE_TYPES as string[]).includes(type)
+}
+
+/** Build the Z-Wave ID/Vendor/Model property rows shown in the right panel.
+ * Matches backend `build_zwave_properties` (no LQI — Z-Wave has none). */
+export function buildZwaveProperties(input: {
+  ieee_address?: string | null
+  vendor?: string | null
+  model?: string | null
+}): NodeProperty[] {
+  const props: NodeProperty[] = []
+  if (input.ieee_address) props.push({ key: 'Z-Wave ID', value: input.ieee_address, icon: null, visible: false })
+  if (input.vendor) props.push({ key: 'Vendor', value: input.vendor, icon: null, visible: false })
+  if (input.model) props.push({ key: 'Model', value: input.model, icon: null, visible: false })
+  return props
+}