* sftpd: use global TLS-aware HTTP client for filer uploads (#8794)
putFile() hardcoded http:// and used http.DefaultClient, which broke
file uploads when the filer has HTTPS/TLS enabled. Switch to the global
HTTP client which reads [https.client] from security.toml and
automatically normalizes the URL scheme.
* sftpd: propagate NormalizeUrl error instead of swallowing it