feat: collaboration temps reel - edition simultanee (#62)

WebSocket /ws/collab/{vault}/{path} (rooms par fichier), relais Yjs/CRDT, awareness (curseurs colores + presence), persistance serveur debounce 2s, auth WS + check_vault_access, reconnexion automatique. Frontend frontend/js/collab.js, backend backend/collab.py. Tests: 17 backend (5 clients simultanes) + 10 frontend. Docs: CHANGELOG, ROADMAP, fiche features/collaboration.md, README FR/EN.

backend/main.py

@@ -19,13 +19,14 @@ from typing import Any
 
 import frontmatter
 import mistune
-from fastapi import Body, Depends, FastAPI, HTTPException, Query, Request
+from fastapi import Body, Depends, FastAPI, HTTPException, Query, Request, WebSocket
 from fastapi.responses import FileResponse, HTMLResponse, JSONResponse, Response, StreamingResponse
 from fastapi.staticfiles import StaticFiles
 from pydantic import BaseModel, Field
 from starlette.middleware.base import BaseHTTPMiddleware
 
 from backend.attachment_indexer import get_attachment_stats, rescan_vault_attachments
+from backend.collab import authenticate_websocket, collab_manager
 from backend.history import (
     get_bookmarks,
     record_open,
@@ -739,6 +740,7 @@ async def lifespan(app: FastAPI):
     yield
 
     # Shutdown
+    await collab_manager.stop()
     if _vault_watcher:
         await _vault_watcher.stop()
         _vault_watcher = None
@@ -4091,6 +4093,48 @@ async def api_conflict_resolve(body: dict = Body(...), current_user=Depends(requ
         raise HTTPException(500, f"Error resolving conflict: {e!s}")
 
 
+# ---------------------------------------------------------------------------
+# Real-time collaboration — WebSocket endpoint (ROADMAP #62)
+# ---------------------------------------------------------------------------
+
+@app.websocket("/ws/collab/{vault_name}/{path:path}")
+async def collab_websocket(websocket: WebSocket, vault_name: str, path: str):
+    """Real-time collaborative editing over WebSocket (ROADMAP #62).
+
+    One *room* is created per ``vault::path``; all clients editing the same
+    file share Yjs/CRDT updates, awareness (cursors/selection) and a debounced
+    server-side persistence of the markdown content.
+
+    Authentication is performed manually (FastAPI ``Depends`` do not run for
+    WebSocket routes) and vault access is enforced per connection.
+    """
+    from backend.services.errors import ServiceError
+    from backend.services.vaults import get_vault_root
+
+    user = authenticate_websocket(websocket)
+    if user is None:
+        await websocket.close(code=4401)
+        return
+
+    if not check_vault_access(vault_name, user):
+        await websocket.close(code=4403)
+        return
+
+    try:
+        vault_root = get_vault_root(vault_name)
+        file_path = _resolve_safe_path(vault_root, path)
+    except ServiceError:
+        await websocket.close(code=4404)
+        return
+
+    if not file_path.exists() or not file_path.is_file():
+        await websocket.close(code=4404)
+        return
+
+    await websocket.accept()
+    await collab_manager.connect(websocket, vault_name, path, file_path, user)
+
+
 # ---------------------------------------------------------------------------
 # Static files & SPA fallback
 # ---------------------------------------------------------------------------