add diaposine

client/src/app/App.tsx

@@ -4,6 +4,7 @@ import { AppRoutes } from '@/app/routes'
 import { NotificationStack } from '@/shared/ui/NotificationStack'
 import { ErrorBoundary } from '@/shared/ui/ErrorBoundary'
 import { NoiseOverlay } from '@/shared/ui/NoiseOverlay'
+import { DemoOverlay } from '@/shared/ui/DemoOverlay'
 
 export function App() {
   return (
@@ -14,6 +15,7 @@ export function App() {
         </ErrorBoundary>
         <NotificationStack />
         <NoiseOverlay />
+        <DemoOverlay />
       </BrowserRouter>
     </AppProviders>
   )

client/src/shared/ui/DemoOverlay.tsx

@@ -0,0 +1,56 @@
+import Box from '@mui/material/Box'
+import { useTheme } from '@mui/material/styles'
+import { IS_DEMO_MODE } from '@/shared/config'
+
+export function DemoOverlay() {
+  const theme = useTheme()
+  const isDark = theme.palette.mode === 'dark'
+
+  if (!IS_DEMO_MODE) return null
+
+  return (
+    <>
+      <Box
+        aria-hidden="true"
+        sx={{
+          position: 'fixed',
+          inset: 0,
+          display: 'flex',
+          alignItems: 'center',
+          justifyContent: 'center',
+          pointerEvents: 'none',
+          zIndex: 9990,
+          fontSize: '10vw',
+          fontWeight: 900,
+          color: isDark ? 'rgba(255,255,255,0.04)' : 'rgba(0,0,0,0.04)',
+          transform: 'rotate(-30deg)',
+          userSelect: 'none',
+        }}
+      >
+        ДЕМО
+      </Box>
+
+      <Box
+        aria-hidden="true"
+        sx={{
+          position: 'fixed',
+          bottom: 16,
+          right: 16,
+          pointerEvents: 'none',
+          zIndex: 9991,
+          px: 2,
+          py: 0.75,
+          borderRadius: 1,
+          fontSize: 12,
+          fontWeight: 600,
+          letterSpacing: '0.04em',
+          color: isDark ? 'rgba(255,255,255,0.6)' : '#fff',
+          bgcolor: isDark ? 'rgba(255,255,255,0.08)' : 'rgba(0,0,0,0.6)',
+          userSelect: 'none',
+        }}
+      >
+        ДЕМО-РЕЖИМ
+      </Box>
+    </>
+  )
+}

client/src/shared/ui/__tests__/DemoOverlay.test.tsx

@@ -0,0 +1,44 @@
+import { render } from '@testing-library/react'
+import { describe, expect, it, vi } from 'vitest'
+
+let mockDemoMode = true
+
+vi.mock('@/shared/config', async () => {
+  const actual = await vi.importActual<typeof import('@/shared/config')>('@/shared/config')
+  return {
+    ...actual,
+    get IS_DEMO_MODE() {
+      return mockDemoMode
+    },
+  }
+})
+
+import { DemoOverlay } from '../DemoOverlay'
+
+describe('DemoOverlay', () => {
+  it('рендерит водяной знак и плашку когда демо включён', () => {
+    mockDemoMode = true
+    const { container } = render(<DemoOverlay />)
+
+    const text = container.textContent
+    expect(text).toContain('ДЕМО')
+    expect(text).toContain('ДЕМО-РЕЖИМ')
+
+    const allBoxes = container.querySelectorAll('.MuiBox-root')
+    expect(allBoxes.length).toBeGreaterThanOrEqual(2)
+
+    const [watermark, badge] = allBoxes
+
+    expect(watermark.getAttribute('aria-hidden')).toBe('true')
+    expect(watermark.textContent).toBe('ДЕМО')
+
+    expect(badge.getAttribute('aria-hidden')).toBe('true')
+    expect(badge.textContent).toBe('ДЕМО-РЕЖИМ')
+  })
+
+  it('не рендерит ничего когда демо выключен', () => {
+    mockDemoMode = false
+    const { container } = render(<DemoOverlay />)
+    expect(container.textContent).toBe('')
+  })
+})