server {
    listen 8081;
    server_name _;

    root /usr/share/nginx/html;
    index index.html;

    # SPA fallback — tailscale serve strips the /flowchart/ mount point,
    # so nginx receives /assets/... and / (index.html)
    location / {
        try_files $uri $uri/ /index.html;
    }
}