- Change password parameter from &str to String in add_proxmox_cluster
so Tauri v2 IPC can deserialize it (requires DeserializeOwned + Send)
- Construct full https:// URL with port in ProxmoxClient::get_api_url()
and authenticate() since the frontend strips the protocol before
sending the hostname
- Show actual error string in AddRemoteForm instead of generic fallback
(Tauri errors are plain strings, not Error instances)
- Update client tests to reflect bare-hostname input from the frontend
