fix: update fallback service to serve index.html for not found routes

src/main.rs

@@ -1,10 +1,13 @@
 use axum::Router;
-use tower_http::services::ServeDir;
+use tower_http::services::{ServeDir, ServeFile};
 
 #[shuttle_runtime::main]
 #[allow(clippy::unused_async)]
 async fn main() -> shuttle_axum::ShuttleAxum {
-    let router = Router::new().fallback_service(ServeDir::new("frontend/dist/frontend/browser"));
+    let router = Router::new().fallback_service(
+        ServeDir::new("frontend/dist/frontend/browser")
+            .not_found_service(ServeFile::new("frontend/dist/frontend/browser/index.html")),
+    );
 
     Ok(router.into())
 }