feat: add UI-only group node types and enhance workflow graph processing

web/app/components/workflow/custom-group-node/custom-group-input-node.tsx

@@ -0,0 +1,55 @@
+'use client'
+
+import type { FC } from 'react'
+import { memo } from 'react'
+import { Handle, Position } from 'reactflow'
+import type { CustomGroupInputNodeData } from './types'
+import cn from '@/utils/classnames'
+
+type CustomGroupInputNodeProps = {
+  id: string
+  data: CustomGroupInputNodeData
+}
+
+const CustomGroupInputNode: FC<CustomGroupInputNodeProps> = ({ id: _id, data }) => {
+  return (
+    <div
+      className={cn(
+        'flex items-center justify-center',
+        'h-8 w-8 rounded-full',
+        'bg-util-colors-blue-blue-500 shadow-md',
+        data.selected && 'ring-2 ring-primary-400',
+      )}
+    >
+      {/* Target handle - receives external connections */}
+      <Handle
+        id="target"
+        type="target"
+        position={Position.Left}
+        className="!h-2 !w-2 !border-0 !bg-white"
+      />
+
+      {/* Source handle - connects to entry nodes */}
+      <Handle
+        id="source"
+        type="source"
+        position={Position.Right}
+        className="!h-2 !w-2 !border-0 !bg-white"
+      />
+
+      {/* Icon */}
+      <svg
+        className="h-4 w-4 text-white"
+        viewBox="0 0 24 24"
+        fill="none"
+        stroke="currentColor"
+        strokeWidth={2}
+      >
+        <path d="M9 12l2 2 4-4" />
+        <circle cx="12" cy="12" r="10" />
+      </svg>
+    </div>
+  )
+}
+
+export default memo(CustomGroupInputNode)