feat(network): add group/ungroup commands with bounding box calculation

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/components/network/nodes/GroupNode.tsx

@@ -1,5 +1,5 @@
 import { memo, useState, useRef, useEffect } from 'react'
-import { NodeProps, NodeResizer, useReactFlow } from '@xyflow/react'
+import { NodeResizer, useReactFlow, type NodeProps } from '@xyflow/react'
 import type { GroupNodeData } from '@/types/network-diagram'
 
 const GROUP_COLORS: Record<string, string> = {