feat: CRUD UI — race form, detail fields, edit/delete actions

- RaceDetailsPage: show all non-null fields (officialUrl, startTime, clusterSchedule, bibPickup)

- RaceDetailsPage: add edit link and delete button with confirmation banner

- RaceFormPage: universal create/edit form with validation, auto-generated id for new races

- Router: add /races/new and /races/:raceId/edit routes

- AppLayout: add navigation link to create new race

- CSS: buttons (primary/secondary/danger), form fields, confirm banner, responsive layout

Made-with: Cursor

frontend/src/app/router.tsx

@@ -3,6 +3,7 @@ import { AppLayout } from "./layouts/AppLayout";
 import { DashboardPage } from "../pages/DashboardPage";
 import { RacesPage } from "../pages/RacesPage";
 import { RaceDetailsPage } from "../pages/RaceDetailsPage";
+import { RaceFormPage } from "../pages/RaceFormPage";
 
 export const appRouter = createBrowserRouter([
   {
@@ -11,7 +12,9 @@ export const appRouter = createBrowserRouter([
     children: [
       { index: true, element: <DashboardPage /> },
       { path: "races", element: <RacesPage /> },
+      { path: "races/new", element: <RaceFormPage /> },
       { path: "races/:raceId", element: <RaceDetailsPage /> },
+      { path: "races/:raceId/edit", element: <RaceFormPage /> },
     ],
   },
 ]);