fix(frontend): leptos 0.8 migration fixes - Callback::run, StoredValue::new_local, traits

frontend/src/app.rs

@@ -9,6 +9,7 @@ use leptos::logging;
 use leptos::task::spawn_local;
 use leptos_router::components::{Router, Routes, Route};
 use leptos_router::hooks::use_navigate;
+// use leptos_router::PossibleRouteMatch; // Bu trait prelude ile gelmeli veya public olmayabilir.
 
 #[component]
 pub fn App() -> impl IntoView {