M7-T06: add meter management UI (timeline, declare swap, edit) to Energy view

frontend/src/pages/EnergyPage.test.tsx

@@ -381,6 +381,44 @@ describe('EnergyPage — test-read', () => {
   })
 })
 
+describe('EnergyPage — meters tab', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+    setupDefaultMocks()
+  })
+
+  it('renders Meters tab in the tab list', async () => {
+    renderEnergy()
+
+    await waitFor(() => {
+      expect(screen.getByTestId('tab-meters')).toBeInTheDocument()
+    })
+    expect(screen.getByTestId('tab-meters').textContent).toContain('Meters')
+  })
+
+  it('renders meters panel when Meters tab is clicked', async () => {
+    mockGet.mockImplementation((path: string) => {
+      if (path === '/api/modbus/devices') {
+        return Promise.resolve({ data: { items: [DEVICE], total: 1 } })
+      }
+      if (path === '/api/energy/meters') {
+        return Promise.resolve({ data: { items: [], total: 0 } })
+      }
+      return Promise.resolve({ data: null })
+    })
+
+    renderEnergy()
+
+    await waitFor(() => expect(screen.getByTestId('tab-meters')).toBeInTheDocument())
+
+    fireEvent.click(screen.getByTestId('tab-meters'))
+
+    await waitFor(() => {
+      expect(screen.getByTestId('panel-meters')).toBeInTheDocument()
+    })
+  })
+})
+
 describe('EnergyPage — auto-refresh switch', () => {
   beforeEach(() => {
     vi.clearAllMocks()