feat: configurable bottom handles, scanner rewrite, UI polish

## New features
- Configurable bottom connection points per node (1–4 handles)
- Fit view on load
- LiveView improvements
- Node modal: inline Type/Icon picker, default icon in trigger
- Remove redundant Save button from ScanConfigModal

## Scanner fixes
- Phase 1: replace nmap ARP sweep with concurrent asyncio ping sweep
  (50 parallel pings, 1s timeout). Zero false positives, works in any
  Docker network mode. Supplements with /proc/net/arp for ICMP-blocked devices.
- Phase 2: explicit -sS (root) / -sT (non-root) scan type; bump
  host-timeout to 60s; gather(return_exceptions=True) so one failing
  host doesn't abort the batch
- Fix 404 on missing device in hide/ignore
- Validate CIDR ranges to prevent nmap injection
- Thread-safe cancel set, pre-fetch canvas/hidden IPs (no N+1 queries)
- Logging: attach StreamHandler to root logger so app.* logs are visible

## Tests
- 21 backend scanner tests (ping sweep, ARP cache, Phase 2 tolerance)
- Full NodeModal coverage (53 tests)
- LiveView, store, edge label tests

frontend/src/components/__tests__/LiveView.test.tsx

@@ -11,6 +11,7 @@ vi.mock('@xyflow/react', () => ({
   Controls: () => null,
   BackgroundVariant: { Dots: 'dots' },
   ConnectionMode: { Loose: 'loose' },
+  useReactFlow: () => ({ fitView: vi.fn() }),
 }))
 vi.mock('@xyflow/react/dist/style.css', () => ({}))
 
@@ -50,6 +51,8 @@ describe('LiveView (non-standalone)', () => {
     useCanvasStore.setState({ nodes: [], edges: [] })
   })
 
+  afterEach(() => { setSearch('') })
+
   // ── No key ────────────────────────────────────────────────────────────────
 
   it('shows no-key error when ?key= is missing', async () => {
@@ -133,11 +136,25 @@ describe('LiveView (non-standalone)', () => {
 
 // ── Standalone mode ────────────────────────────────────────────────────────
 
+const XYFLOW_MOCK = {
+  ReactFlowProvider: ({ children }: { children: React.ReactNode }) => <>{children}</>,
+  ReactFlow: () => <div data-testid="react-flow" />,
+  Background: () => null,
+  Controls: () => null,
+  BackgroundVariant: { Dots: 'dots' },
+  ConnectionMode: { Loose: 'loose' },
+  useReactFlow: () => ({ fitView: vi.fn() }),
+}
+
 describe('LiveView (standalone — localStorage)', () => {
   beforeEach(() => {
     localStorage.clear()
     useCanvasStore.setState({ nodes: [], edges: [] })
-    vi.mocked(liveviewApi.load).mockReset()
+  })
+
+  afterEach(() => {
+    setSearch('')
+    vi.unstubAllEnvs()
   })
 
   it('loads canvas from localStorage without calling the API', async () => {
@@ -151,25 +168,12 @@ describe('LiveView (standalone — localStorage)', () => {
     }
     localStorage.setItem('homelable_canvas', JSON.stringify(stored))
 
-    // Stub VITE_STANDALONE before re-importing
-    vi.stubEnv('VITE_STANDALONE', 'true')
-    vi.resetModules()
-    const { default: LiveViewStandalone } = await import('../LiveView')
-
-    setSearch('')  // no key needed in standalone
-    render(<LiveViewStandalone />)
-
-    await waitFor(() => {
-      expect(screen.getByTestId('react-flow')).toBeDefined()
-    })
-    expect(liveviewApi.load).not.toHaveBeenCalled()
-
-    vi.unstubAllEnvs()
-  })
-
-  it('shows canvas (empty) when localStorage has no saved data', async () => {
     vi.stubEnv('VITE_STANDALONE', 'true')
     vi.resetModules()
+    const mockLoad = vi.fn()
+    vi.doMock('@xyflow/react', () => XYFLOW_MOCK)
+    vi.doMock('@xyflow/react/dist/style.css', () => ({}))
+    vi.doMock('@/api/client', () => ({ liveviewApi: { load: mockLoad } }))
     const { default: LiveViewStandalone } = await import('../LiveView')
 
     setSearch('')
@@ -178,8 +182,24 @@ describe('LiveView (standalone — localStorage)', () => {
     await waitFor(() => {
       expect(screen.getByTestId('react-flow')).toBeDefined()
     })
-    expect(liveviewApi.load).not.toHaveBeenCalled()
+    expect(mockLoad).not.toHaveBeenCalled()
+  })
 
-    vi.unstubAllEnvs()
+  it('shows canvas (empty) when localStorage has no saved data', async () => {
+    vi.stubEnv('VITE_STANDALONE', 'true')
+    vi.resetModules()
+    const mockLoad = vi.fn()
+    vi.doMock('@xyflow/react', () => XYFLOW_MOCK)
+    vi.doMock('@xyflow/react/dist/style.css', () => ({}))
+    vi.doMock('@/api/client', () => ({ liveviewApi: { load: mockLoad } }))
+    const { default: LiveViewStandalone } = await import('../LiveView')
+
+    setSearch('')
+    render(<LiveViewStandalone />)
+
+    await waitFor(() => {
+      expect(screen.getByTestId('react-flow')).toBeDefined()
+    })
+    expect(mockLoad).not.toHaveBeenCalled()
   })
 })