feat(J): WebSocket live-events + replace polling + fix ffmpeg turntable timeout

- fix(render): ffmpeg overlay=0:0 -> overlay=0:0:shortest=1 to prevent hang on finite PNG sequences
- feat(ws): add core/websocket.py ConnectionManager + Redis Pub/Sub subscriber loop
- feat(ws): add /api/ws WebSocket endpoint with JWT query-param auth in main.py
- feat(ws): emit render_complete/failed + cad_processing_complete events from step_tasks.py
- feat(ws): emit order_status_change events from orders router
- feat(ws): add beat_tasks.py broadcast_queue_status task (every 10s via Redis __broadcast__)
- feat(frontend): add useWebSocket hook with auto-reconnect (exponential backoff, 25s ping)
- feat(frontend): add WebSocketContext + WebSocketProvider wrapping App
- refactor(frontend): remove polling from WorkerActivity (was 5s/3s) + OrderDetail (was 5s)
- refactor(frontend): reduce polling in Layout (8s->60s) + NotificationCenter (15s->60s)
- docs: add ffmpeg shortest=1 + WebSocket JWT auth learnings to LEARNINGS.md

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/App.tsx

@@ -1,5 +1,6 @@
 import { BrowserRouter, Routes, Route, Navigate } from 'react-router-dom'
 import { useAuthStore } from './store/auth'
+import { WebSocketProvider } from './contexts/WebSocketContext'
 import Layout from './components/layout/Layout'
 import LoginPage from './pages/Login'
 import DashboardPage from './pages/Dashboard'
@@ -38,7 +39,8 @@ function AdminRoute({ children }: { children: React.ReactNode }) {
 export default function App() {
   return (
     <BrowserRouter>
-      <Routes>
+      <WebSocketProvider>
+        <Routes>
         <Route path="/login" element={<LoginPage />} />
         <Route
           path="/"
@@ -103,7 +105,8 @@ export default function App() {
             }
           />
         </Route>
-      </Routes>
+        </Routes>
+      </WebSocketProvider>
     </BrowserRouter>
   )
 }