feat(group): add 4 side handles for edge connections

Group nodes can now be source/target of edges via snap points on
each side (top/right/bottom/left). Each side exposes a source handle
plus an invisible target overlay, matching the pattern used by
BaseNode.

frontend/src/components/canvas/__tests__/GroupNode.test.tsx

@@ -11,6 +11,8 @@ vi.mock('@xyflow/react', () => ({
   NodeResizer: ({ isVisible }: { isVisible: boolean }) => (
     <div data-testid="node-resizer" data-visible={isVisible} />
   ),
+  Handle: () => null,
+  Position: { Top: 'top', Right: 'right', Bottom: 'bottom', Left: 'left' },
   useReactFlow: () => ({}),
 }))
 

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

@@ -1,11 +1,15 @@
 import { useState } from 'react'
-import { type NodeProps, type Node, NodeResizer } from '@xyflow/react'
+import { type NodeProps, type Node, NodeResizer, Handle, Position } from '@xyflow/react'
 import { Layers, Pencil, Check, X } from 'lucide-react'
 import { useCanvasStore } from '@/stores/canvasStore'
+import { useThemeStore } from '@/stores/themeStore'
+import { THEMES } from '@/utils/themes'
 import { STATUS_COLORS, type NodeData } from '@/types'
 
 export function GroupNode({ id, data, selected }: NodeProps<Node<NodeData>>) {
   const { nodes, updateNode, snapshotHistory } = useCanvasStore()
+  const activeTheme = useThemeStore((s) => s.activeTheme)
+  const theme = THEMES[activeTheme]
   const showBorder = data.custom_colors?.show_border !== false
   const isVisible = showBorder || selected
 
@@ -49,6 +53,29 @@ export function GroupNode({ id, data, selected }: NodeProps<Node<NodeData>>) {
         handleStyle={{ fill: '#00d4ff', stroke: '#0d1117', width: 8, height: 8, borderRadius: 2 }}
       />
 
+      {/* 4 snap-point handles — one per side. Source + invisible target overlay for each. */}
+      {([
+        ['group-top', Position.Top],
+        ['group-right', Position.Right],
+        ['group-bottom', Position.Bottom],
+        ['group-left', Position.Left],
+      ] as const).map(([hid, pos]) => (
+        <span key={hid}>
+          <Handle
+            type="source"
+            position={pos}
+            id={hid}
+            style={{ background: theme.colors.handleBackground, borderColor: theme.colors.handleBorder }}
+          />
+          <Handle
+            type="target"
+            position={pos}
+            id={`${hid}-t`}
+            style={{ opacity: 0, width: 12, height: 12 }}
+          />
+        </span>
+      ))}
+
       {/* Header */}
       {isVisible && (
         <div

frontend/src/components/canvas/nodes/__tests__/GroupNode.test.tsx

@@ -0,0 +1,81 @@
+import { describe, it, expect, beforeEach } from 'vitest'
+import { render } from '@testing-library/react'
+import { ReactFlowProvider } from '@xyflow/react'
+import { GroupNode } from '../GroupNode'
+import { useCanvasStore } from '@/stores/canvasStore'
+import { useThemeStore } from '@/stores/themeStore'
+import type { NodeData } from '@/types'
+import type { NodeProps, Node } from '@xyflow/react'
+
+function renderNode(data: Partial<NodeData> = {}, selected = false) {
+  const fullData: NodeData = {
+    label: 'Group A',
+    type: 'group',
+    status: 'unknown',
+    services: [],
+    ...data,
+  }
+  const props = {
+    id: 'g1',
+    data: fullData,
+    selected,
+    type: 'group',
+    zIndex: 0,
+    isConnectable: true,
+    xPos: 0,
+    yPos: 0,
+    dragging: false,
+    deletable: true,
+    draggable: true,
+    selectable: true,
+    positionAbsoluteX: 0,
+    positionAbsoluteY: 0,
+    width: 300,
+    height: 200,
+    dragHandle: undefined,
+    parentId: undefined,
+    sourcePosition: undefined,
+    targetPosition: undefined,
+  } as unknown as NodeProps<Node<NodeData>>
+  return render(
+    <ReactFlowProvider>
+      <GroupNode {...props} />
+    </ReactFlowProvider>
+  )
+}
+
+describe('GroupNode', () => {
+  beforeEach(() => {
+    useCanvasStore.setState({ nodes: [], hideIp: false })
+    useThemeStore.setState({ activeTheme: 'default' })
+  })
+
+  it('renders label', () => {
+    const { getByText } = renderNode({ label: 'My Group' })
+    expect(getByText('My Group')).toBeDefined()
+  })
+
+  it('renders 4 source handles (one per side)', () => {
+    const { container } = renderNode()
+    expect(container.querySelector('.react-flow__handle-top.source')).not.toBeNull()
+    expect(container.querySelector('.react-flow__handle-right.source')).not.toBeNull()
+    expect(container.querySelector('.react-flow__handle-bottom.source')).not.toBeNull()
+    expect(container.querySelector('.react-flow__handle-left.source')).not.toBeNull()
+  })
+
+  it('renders 4 target handles (one per side)', () => {
+    const { container } = renderNode()
+    expect(container.querySelector('.react-flow__handle-top.target')).not.toBeNull()
+    expect(container.querySelector('.react-flow__handle-right.target')).not.toBeNull()
+    expect(container.querySelector('.react-flow__handle-bottom.target')).not.toBeNull()
+    expect(container.querySelector('.react-flow__handle-left.target')).not.toBeNull()
+  })
+
+  it('source handles carry side-specific ids', () => {
+    const { container } = renderNode()
+    expect(container.querySelector('[data-handleid="group-top"]')).not.toBeNull()
+    expect(container.querySelector('[data-handleid="group-right"]')).not.toBeNull()
+    expect(container.querySelector('[data-handleid="group-bottom"]')).not.toBeNull()
+    expect(container.querySelector('[data-handleid="group-left"]')).not.toBeNull()
+  })
+})