feat: replace static hardware fields with dynamic node properties

Replaces the 4 fixed hardware columns (cpu_count, cpu_model, ram_gb,
disk_gb) with a flexible properties system. Each property has a key,
value, icon (from a curated Lucide picker), and a visibility toggle
that controls whether it appears on the canvas node card.

- Backend: add `properties` JSON column to Node model; data migration
  converts existing hardware rows to properties with correct icons
  (idempotent, old columns kept for safety)
- Backend: add `properties` to NodeBase, NodeUpdate, NodeSave schemas
  and canvasSerializer so values survive canvas save/load
- Frontend: add NodeProperty type; new propertyIcons.ts registry (20
  icons); BaseNode renders visible properties with legacy hardware
  fallback for unmigrated nodes
- Frontend: DetailPanel gains interactive properties section (add /
  edit / remove / toggle visibility / icon picker) replacing the
  read-only hardware block; hardware section removed from NodeModal
- Tests: 6 migration tests, 7 API tests, 8 DetailPanel property tests,
  6 BaseNode render/fallback tests, 9 propertyIcons util tests

frontend/src/components/modals/__tests__/NodeModal.test.tsx

@@ -293,91 +293,6 @@ describe('NodeModal', () => {
     expect(screen.getByText(/Using default colors for/)).toBeDefined()
   })
 
-  // ── Hardware section ──────────────────────────────────────────────────
-
-  it('renders Hardware toggle button', () => {
-    renderModal()
-    expect(screen.getByText('Hardware')).toBeDefined()
-  })
-
-  it('hardware fields are hidden by default', () => {
-    renderModal()
-    expect(screen.queryByPlaceholderText('e.g. Intel Xeon E5-2680')).toBeNull()
-  })
-
-  it('expands hardware fields on toggle click', () => {
-    renderModal()
-    fireEvent.click(screen.getByText('Hardware'))
-    expect(screen.getByPlaceholderText('e.g. Intel Xeon E5-2680')).toBeDefined()
-    expect(screen.getByPlaceholderText('e.g. 8')).toBeDefined()
-    expect(screen.getByPlaceholderText('e.g. 32')).toBeDefined()
-    expect(screen.getByPlaceholderText('e.g. 500')).toBeDefined()
-  })
-
-  it('auto-expands when initial has hardware data', () => {
-    renderModal({ initial: { ...BASE, cpu_count: 8, ram_gb: 32 } })
-    expect(screen.getByPlaceholderText('e.g. Intel Xeon E5-2680')).toBeDefined()
-  })
-
-  it('pre-fills hardware fields from initial', () => {
-    renderModal({ initial: { ...BASE, cpu_model: 'Intel i5', cpu_count: 4, ram_gb: 16, disk_gb: 500 } })
-    expect((screen.getByPlaceholderText('e.g. Intel Xeon E5-2680') as HTMLInputElement).value).toBe('Intel i5')
-  })
-
-  it('submits hardware fields when filled', () => {
-    const { onSubmit } = renderModal()
-    fireEvent.change(screen.getByPlaceholderText('My Server'), { target: { value: 'Homelab' } })
-    fireEvent.click(screen.getByText('Hardware'))
-    fireEvent.change(screen.getByPlaceholderText('e.g. Intel Xeon E5-2680'), { target: { value: 'Intel i7-12700K' } })
-    fireEvent.change(screen.getByPlaceholderText('e.g. 8'), { target: { value: '12' } })
-    fireEvent.change(screen.getByPlaceholderText('e.g. 32'), { target: { value: '64' } })
-    fireEvent.change(screen.getByPlaceholderText('e.g. 500'), { target: { value: '2000' } })
-    fireEvent.click(screen.getByRole('button', { name: 'Add' }))
-    const data = onSubmit.mock.calls[0][0] as Partial<NodeData>
-    expect(data.cpu_model).toBe('Intel i7-12700K')
-    expect(data.cpu_count).toBe(12)
-    expect(data.ram_gb).toBe(64)
-    expect(data.disk_gb).toBe(2000)
-  })
-
-  it('hides Hardware section for groupRect type', () => {
-    renderModal({ initial: { type: 'groupRect' } })
-    expect(screen.queryByText('Hardware')).toBeNull()
-  })
-
-  it('show_hardware toggle hidden when section is collapsed', () => {
-    renderModal()
-    expect(screen.queryByText('Show on node')).toBeNull()
-  })
-
-  it('show_hardware toggle appears when section is expanded', () => {
-    renderModal()
-    fireEvent.click(screen.getByText('Hardware'))
-    expect(screen.getByText('Show on node')).toBeDefined()
-  })
-
-  it('show_hardware defaults to falsy', () => {
-    const { onSubmit } = renderModal()
-    fireEvent.change(screen.getByPlaceholderText('My Server'), { target: { value: 'Node' } })
-    fireEvent.click(screen.getByRole('button', { name: 'Add' }))
-    expect(onSubmit.mock.calls[0][0].show_hardware).toBeFalsy()
-  })
-
-  it('toggling show_hardware sets it to true', () => {
-    const { onSubmit } = renderModal()
-    fireEvent.change(screen.getByPlaceholderText('My Server'), { target: { value: 'Node' } })
-    fireEvent.click(screen.getByText('Hardware'))
-    fireEvent.click(screen.getByRole('switch'))
-    fireEvent.click(screen.getByRole('button', { name: 'Add' }))
-    expect(onSubmit.mock.calls[0][0].show_hardware).toBe(true)
-  })
-
-  it('pre-fills show_hardware from initial', () => {
-    const { onSubmit } = renderModal({ initial: { label: 'Node', show_hardware: true, cpu_count: 8 } })
-    fireEvent.click(screen.getByRole('button', { name: 'Add' }))
-    expect(onSubmit.mock.calls[0][0].show_hardware).toBe(true)
-  })
-
   // ── Bottom connection points ───────────────────────────────────────────
 
   it('shows Bottom Connection Points for server type', () => {