feat(sse): sync temps réel multi-appareils via Server-Sent Events v0.5.8

- Broadcaster asyncio.Queue avec keepalive 25s (prévient timeout proxy)
- Endpoint GET /api/events/stream (StreamingResponse text/event-stream)
- Broadcast notes_changed / todos_changed / shopping_changed sur toutes mutations
- Hook useServerEvents: EventSource avec reconnexion automatique (3s)
- Pages Notes, Todos, Shopping abonnées aux événements SSE
- nginx: location SSE dédiée (proxy_buffering off, timeout 24h)

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

frontend/nginx.conf

@@ -14,6 +14,17 @@ server {
         add_header Cache-Control "public, immutable";
     }
 
+    location /api/events/stream {
+        proxy_pass http://backend:8000/api/events/stream;
+        proxy_set_header Host $host;
+        proxy_set_header X-Real-IP $remote_addr;
+        proxy_http_version 1.1;
+        proxy_set_header Connection "";
+        proxy_buffering off;
+        proxy_cache off;
+        proxy_read_timeout 86400s;
+    }
+
     location /api/ {
         proxy_pass http://backend:8000/api/;
         proxy_set_header Host $host;