fix: DEL key deletes nodes and deletion is now undoable

- Add 'Delete' to deleteKeyCode so both Backspace and Delete remove nodes
- Call snapshotHistory() in onBeforeDelete (keyboard) and in DetailPanel
  handleDelete (button) so deletions can be undone with Ctrl+Z

frontend/src/components/canvas/CanvasContainer.tsx

@@ -27,7 +27,7 @@ export function CanvasContainer({ onConnect: onConnectProp, onEdgeDoubleClick, o
   const {
     nodes, edges,
     onNodesChange, onEdgesChange,
-    setSelectedNode,
+    setSelectedNode, snapshotHistory,
   } = useCanvasStore()
 
   const activeTheme = useThemeStore((s) => s.activeTheme)
@@ -59,6 +59,8 @@ export function CanvasContainer({ onConnect: onConnectProp, onEdgeDoubleClick, o
         onNodeDragStart={onNodeDragStart}
         nodeTypes={nodeTypes}
         edgeTypes={edgeTypes}
+        deleteKeyCode={['Backspace', 'Delete']}
+        onBeforeDelete={async () => { snapshotHistory(); return true }}
         snapToGrid
         snapGrid={[16, 16]}
         fitView

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

@@ -143,4 +143,22 @@ describe('CanvasContainer', () => {
     render(<CanvasContainer />)
     expect(rfProps.snapGrid).toEqual([16, 16])
   })
+
+  // ── Delete key ────────────────────────────────────────────────────────────
+
+  it('sets deleteKeyCode to include both Backspace and Delete', () => {
+    render(<CanvasContainer />)
+    expect(rfProps.deleteKeyCode).toEqual(['Backspace', 'Delete'])
+  })
+
+  // ── onBeforeDelete snapshot ───────────────────────────────────────────────
+
+  it('onBeforeDelete calls snapshotHistory and returns true', async () => {
+    const snapshotHistory = vi.fn()
+    useCanvasStore.setState({ snapshotHistory } as unknown as Parameters<typeof useCanvasStore.setState>[0])
+    render(<CanvasContainer />)
+    const result = await (rfProps.onBeforeDelete as () => Promise<boolean>)()
+    expect(snapshotHistory).toHaveBeenCalledOnce()
+    expect(result).toBe(true)
+  })
 })

frontend/src/components/panels/DetailPanel.tsx

@@ -15,7 +15,7 @@ type SvcForm = { port: string; protocol: 'tcp' | 'udp'; service_name: string }
 const EMPTY_FORM: SvcForm = { port: '', protocol: 'tcp', service_name: '' }
 
 export function DetailPanel({ onEdit }: DetailPanelProps) {
-  const { nodes, selectedNodeId, setSelectedNode, deleteNode, updateNode } = useCanvasStore()
+  const { nodes, selectedNodeId, setSelectedNode, deleteNode, updateNode, snapshotHistory } = useCanvasStore()
   const node = nodes.find((n) => n.id === selectedNodeId)
 
   const [addingForNode, setAddingForNode] = useState<string | null>(null)
@@ -35,6 +35,7 @@ export function DetailPanel({ onEdit }: DetailPanelProps) {
 
   const handleDelete = () => {
     if (confirm(`Delete "${data.label}"?`)) {
+      snapshotHistory()
       deleteNode(node.id)
     }
   }

frontend/src/components/panels/__tests__/DetailPanel.test.tsx

@@ -29,6 +29,7 @@ function setupStore(nodeData: Partial<NodeData> = {}) {
     setSelectedNode: vi.fn(),
     deleteNode: vi.fn(),
     updateNode: vi.fn(),
+    snapshotHistory: vi.fn(),
   } as unknown as ReturnType<typeof canvasStore.useCanvasStore>)
 }
 
@@ -40,6 +41,7 @@ describe('DetailPanel', () => {
       setSelectedNode: vi.fn(),
       deleteNode: vi.fn(),
       updateNode: vi.fn(),
+      snapshotHistory: vi.fn(),
     } as unknown as ReturnType<typeof canvasStore.useCanvasStore>)
   })
 
@@ -125,6 +127,7 @@ describe('DetailPanel', () => {
         setSelectedNode,
         deleteNode: vi.fn(),
         updateNode: vi.fn(),
+        snapshotHistory: vi.fn(),
       } as unknown as ReturnType<typeof canvasStore.useCanvasStore>)
       render(<DetailPanel onEdit={vi.fn()} />)
       fireEvent.click(screen.getByLabelText('Close panel'))
@@ -139,33 +142,39 @@ describe('DetailPanel', () => {
       expect(onEdit).toHaveBeenCalledWith('n1')
     })
 
-    it('calls deleteNode when delete confirmed', () => {
+    it('calls snapshotHistory then deleteNode when delete confirmed', () => {
       const deleteNode = vi.fn()
+      const snapshotHistory = vi.fn()
       vi.mocked(canvasStore.useCanvasStore).mockReturnValue({
         nodes: [makeNode({ label: 'My Server' })],
         selectedNodeId: 'n1',
         setSelectedNode: vi.fn(),
         deleteNode,
         updateNode: vi.fn(),
+        snapshotHistory,
       } as unknown as ReturnType<typeof canvasStore.useCanvasStore>)
       vi.spyOn(window, 'confirm').mockReturnValue(true)
       render(<DetailPanel onEdit={vi.fn()} />)
       fireEvent.click(screen.getByLabelText('Delete node'))
+      expect(snapshotHistory).toHaveBeenCalledOnce()
       expect(deleteNode).toHaveBeenCalledWith('n1')
     })
 
-    it('does not call deleteNode when delete is cancelled', () => {
+    it('does not call deleteNode or snapshotHistory when delete is cancelled', () => {
       const deleteNode = vi.fn()
+      const snapshotHistory = vi.fn()
       vi.mocked(canvasStore.useCanvasStore).mockReturnValue({
         nodes: [makeNode({})],
         selectedNodeId: 'n1',
         setSelectedNode: vi.fn(),
         deleteNode,
         updateNode: vi.fn(),
+        snapshotHistory,
       } as unknown as ReturnType<typeof canvasStore.useCanvasStore>)
       vi.spyOn(window, 'confirm').mockReturnValue(false)
       render(<DetailPanel onEdit={vi.fn()} />)
       fireEvent.click(screen.getByLabelText('Delete node'))
+      expect(snapshotHistory).not.toHaveBeenCalled()
       expect(deleteNode).not.toHaveBeenCalled()
     })
   })
@@ -186,6 +195,7 @@ describe('DetailPanel', () => {
         setSelectedNode: vi.fn(),
         deleteNode: vi.fn(),
         updateNode,
+        snapshotHistory: vi.fn(),
       } as unknown as ReturnType<typeof canvasStore.useCanvasStore>)
       render(<DetailPanel onEdit={vi.fn()} />)
       fireEvent.click(screen.getByText('Add'))
@@ -207,6 +217,7 @@ describe('DetailPanel', () => {
         setSelectedNode: vi.fn(),
         deleteNode: vi.fn(),
         updateNode,
+        snapshotHistory: vi.fn(),
       } as unknown as ReturnType<typeof canvasStore.useCanvasStore>)
       render(<DetailPanel onEdit={vi.fn()} />)
       fireEvent.click(screen.getByTitle('Remove service'))
@@ -221,6 +232,7 @@ describe('DetailPanel', () => {
         setSelectedNode: vi.fn(),
         deleteNode: vi.fn(),
         updateNode: vi.fn(),
+        snapshotHistory: vi.fn(),
       } as unknown as ReturnType<typeof canvasStore.useCanvasStore>)
       expect(() => render(<DetailPanel onEdit={vi.fn()} />)).not.toThrow()
     })
@@ -249,6 +261,7 @@ describe('DetailPanel', () => {
         setSelectedNode: vi.fn(),
         deleteNode: vi.fn(),
         updateNode,
+        snapshotHistory: vi.fn(),
       } as unknown as ReturnType<typeof canvasStore.useCanvasStore>)
 
       render(<DetailPanel onEdit={vi.fn()} />)
@@ -271,6 +284,7 @@ describe('DetailPanel', () => {
         setSelectedNode: vi.fn(),
         deleteNode: vi.fn(),
         updateNode,
+        snapshotHistory: vi.fn(),
       } as unknown as ReturnType<typeof canvasStore.useCanvasStore>)
 
       render(<DetailPanel onEdit={vi.fn()} />)