fix : html + css display

backend/src/main.rs

@@ -3,10 +3,13 @@ use std::net::SocketAddr;
 use std::path::Path;
 use tokio::fs::File;
 use tokio::io::{self, AsyncReadExt};
+use tower_http::services::ServeDir;
 
 #[tokio::main]
 async fn main() {
-    let app = Router::new().route("/", get(handler));
+    let app = Router::new()
+        .route("/", get(handler))
+        .nest_service("/assets", ServeDir::new("../web/assets"));
 
     let addr = SocketAddr::from(([127, 0, 0, 1], 3000));
     println!("listening on {}", addr);