modernize: migrate to Leptos 0.8 and Server Functions architecture, break backend->shared loop

shared/src/server_fns/mod.rs

@@ -0,0 +1,26 @@
+use leptos::*;
+use leptos::prelude::*;
+
+#[cfg(feature = "ssr")]
+use crate::xmlrpc::{self, RtorrentClient};
+
+#[server(GetVersion, "/api/server_fns")]
+pub async fn get_version() -> Result<String, ServerFnError> {
+    let socket_path = std::env::var("RTORRENT_SOCKET").unwrap_or_else(|_| "/tmp/rtorrent.sock".to_string());
+    
+    #[cfg(feature = "ssr")]
+    {
+        let client = RtorrentClient::new(&socket_path);
+        match client.call("system.client_version", &[]).await {
+            Ok(xml) => {
+                let version = xmlrpc::parse_string_response(&xml).unwrap_or(xml);
+                Ok(version)
+            },
+            Err(e) => Err(ServerFnError::ServerError(e.to_string())),
+        }
+    }
+    #[cfg(not(feature = "ssr"))]
+    {
+        unreachable!()
+    }
+}