Use 127.0.0.1 as default host

Change the default BUTLER_HOST value from 172.0.0.1 to 127.0.0.1 in crates/but-server/src/lib.rs.

- Updated default host fallback in server initialization to use loopback address 127.0.0.1 instead of 172.0.0.1.
- No other files modified.

This is a focused fix to ensure the server binds to the standard localhost interface by default.

Author: estib-vega

crates/but-server/src/lib.rs

@@ -96,7 +96,7 @@ pub async fn run() {
         .layer(ServiceBuilder::new().layer(cors));
 
     let port = std::env::var("BUTLER_PORT").unwrap_or("6978".into());
-    let host = std::env::var("BUTLER_HOST").unwrap_or("172.0.0.1".into());
+    let host = std::env::var("BUTLER_HOST").unwrap_or("127.0.0.1".into());
     let url = format!("{}:{}", host, port);
     let listener = tokio::net::TcpListener::bind(&url).await.unwrap();
     println!("Running at {}", url);