fix: resolve TypeScript errors in DeviceToolbar and DiagramEditor

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/components/network/panels/DeviceToolbar.tsx

@@ -1,6 +1,5 @@
 import { useState, useMemo, useCallback } from 'react'
 import { Search, Plus, ChevronDown, ChevronRight, X } from 'lucide-react'
-import { cn } from '@/lib/utils'
 import { getDeviceRenderConfig, CATEGORY_LABELS, CATEGORY_ORDER } from '../nodes/deviceRegistry'
 import type { DeviceTypeResponse, DeviceTypeCreate } from '@/types'
 import { deviceTypesApi } from '@/api'