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/components/index.ts

@@ -1 +1,3 @@
 export { PaceTrendChart } from "./PaceTrendChart";
+export { RacesCalendar } from "./RacesCalendar";
+export { StartTimeSelects } from "./StartTimeSelects";