feat: add VNC WebSocket console support for Docker and QEMU nodes

Add VNC console WebSocket endpoints for Docker and QEMU nodes:
- Add /console/vnc WebSocket endpoint to compute API (Docker & QEMU)
- Add /console/vnc WebSocket endpoint to controller API
- Implement start_vnc_websocket_console() in BaseNode
- Forward VNC WebSocket traffic between controller and compute layers

The implementation provides bidirectional WebSocket to TCP forwarding
for VNC protocol (RFB) connections, allowing browser-based VNC console
access to containers and VMs.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

gns3server/api/routes/compute/docker_nodes.py

@@ -384,6 +384,21 @@ async def console_ws(
         await node.start_websocket_console(websocket)
 
 
+@router.websocket(
+    "/{node_id}/console/vnc"
+)
+async def vnc_console_ws(
+        websocket: Union[None, WebSocket] = Depends(ws_compute_authentication),
+        node: DockerVM = Depends(dep_node)
+) -> None:
+    """
+    VNC Console WebSocket.
+    """
+
+    if websocket:
+        await node.start_vnc_websocket_console(websocket)
+
+
 @router.post(
     "/{node_id}/console/reset",
     status_code=status.HTTP_204_NO_CONTENT,