feat(frontend): race form, start time selects, calendar views, day page

- Hide org schedule fields when editing a past race; isRaceDateInPast helper
- StartTimeSelects (HH:mm:ss) and optional ?date= prefill on new race
- Full-card link to edit for races needing result entry; shadow token
- List/calendar toggle (sessionStorage); year grid and month focus views
- Date hover popover and /races/day/:ymd page with Add button
- Docs plan-korrektirovok-starty.md and startTime API note; client 0.4.0

Made-with: Cursor

frontend/src/app/router.tsx

@@ -4,6 +4,7 @@ import { DashboardPage } from "../pages/DashboardPage";
 import { RacesPage } from "../pages/RacesPage";
 import { RaceDetailsPage } from "../pages/RaceDetailsPage";
 import { RaceFormPage } from "../pages/RaceFormPage";
+import { RaceDayPage } from "../pages/RaceDayPage";
 
 export const appRouter = createBrowserRouter([
   {
@@ -13,6 +14,7 @@ export const appRouter = createBrowserRouter([
       { index: true, element: <DashboardPage /> },
       { path: "races", element: <RacesPage /> },
       { path: "races/new", element: <RaceFormPage /> },
+      { path: "races/day/:ymd", element: <RaceDayPage /> },
       { path: "races/:raceId", element: <RaceDetailsPage /> },
       { path: "races/:raceId/edit", element: <RaceFormPage /> },
     ],