feat: setup a backend server with axum

crates/backend/src/main.rs

@@ -0,0 +1,10 @@
+use backend::get_router;
+
+#[tokio::main]
+async fn main() {
+    let app = get_router();
+    let listener = tokio::net::TcpListener::bind("0.0.0.0:8080").await.unwrap();
+
+    println!("Listening on {}", listener.local_addr().unwrap());
+    axum::serve(listener, app).await.unwrap();
+}