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>

backend/app/api/notes.py

@@ -5,6 +5,7 @@ from sqlalchemy import select, text, and_
 from sqlalchemy.ext.asyncio import AsyncSession
 from sqlalchemy.orm import selectinload
 
+from app.core.broadcaster import broadcaster
 from app.core.database import get_session
 from app.core.redis import enqueue
 from app.models.notes import NoteItem, NoteAttachment
@@ -74,6 +75,7 @@ async def create_note(payload: NoteCreate, session: AsyncSession = Depends(get_s
     await session.commit()
     await session.refresh(note, ["attachments"])
     await enqueue("export_note_markdown", str(note.id))
+    broadcaster.broadcast("notes_changed")
     return note
 
 
@@ -97,6 +99,7 @@ async def update_note(
     await session.commit()
     await session.refresh(note, ["attachments"])
     await enqueue("export_note_markdown", str(note.id))
+    broadcaster.broadcast("notes_changed")
     return note
 
 
@@ -108,6 +111,7 @@ async def delete_note(note_id: uuid.UUID, session: AsyncSession = Depends(get_se
     await session.delete(note)
     await session.commit()
     await enqueue("remove_note_markdown", str(note_id))
+    broadcaster.broadcast("notes_changed")
     return Response(status_code=204)
 
 
@@ -151,6 +155,7 @@ async def add_attachment(
     await session.commit()
     await session.refresh(note, ["attachments"])
     await enqueue("export_note_markdown", str(note_id))
+    broadcaster.broadcast("notes_changed")
     return note
 
 
@@ -177,4 +182,5 @@ async def delete_attachment(
     await session.delete(att)
     await session.commit()
     await enqueue("export_note_markdown", str(note_id))
+    broadcaster.broadcast("notes_changed")
     return Response(status_code=204)