feat(network): add undo/redo buttons to DiagramHeader

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

frontend/src/components/network/DiagramHeader.tsx

@@ -1,6 +1,6 @@
 import { useState, useCallback, useRef, useEffect } from 'react'
 import { useNavigate } from 'react-router-dom'
-import { ChevronLeft, Save, Download, FileJson, Image, FileText } from 'lucide-react'
+import { ChevronLeft, Save, Download, FileJson, Image, FileText, Undo2, Redo2 } from 'lucide-react'
 
 interface DiagramHeaderProps {
   name: string
@@ -14,6 +14,10 @@ interface DiagramHeaderProps {
   onExportPng: () => void
   onExportPdf: () => void
   onExportJson: () => void
+  onUndo: () => void
+  onRedo: () => void
+  canUndo: boolean
+  canRedo: boolean
 }
 
 export function DiagramHeader({
@@ -28,6 +32,10 @@ export function DiagramHeader({
   onExportPng,
   onExportPdf,
   onExportJson,
+  onUndo,
+  onRedo,
+  canUndo,
+  canRedo,
 }: DiagramHeaderProps) {
   const navigate = useNavigate()
   const [editing, setEditing] = useState(false)
@@ -88,6 +96,27 @@ export function DiagramHeader({
 
       <div className="mx-2 h-5 w-px bg-border-default" />
 
+      <div className="flex items-center gap-1">
+        <button
+          onClick={onUndo}
+          disabled={!canUndo}
+          title="Undo (Ctrl+Z)"
+          className="p-1.5 rounded text-muted-foreground hover:text-primary hover:bg-elevated disabled:opacity-30 disabled:cursor-not-allowed transition-colors"
+        >
+          <Undo2 size={16} />
+        </button>
+        <button
+          onClick={onRedo}
+          disabled={!canRedo}
+          title="Redo (Ctrl+Y)"
+          className="p-1.5 rounded text-muted-foreground hover:text-primary hover:bg-elevated disabled:opacity-30 disabled:cursor-not-allowed transition-colors"
+        >
+          <Redo2 size={16} />
+        </button>
+      </div>
+
+      <div className="mx-2 h-5 w-px bg-border-default" />
+
       {editing ? (
         <input
           ref={inputRef}