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/lib/index.ts

@@ -6,6 +6,7 @@ export {
   getRaceStatusClassName,
   getRaceStatusLabel,
   isCloseDistance,
+  isRaceDateInPast,
   parseFinishTimeToSeconds,
   parseRaceDate,
   raceNeedsResultEntry,
@@ -13,3 +14,5 @@ export {
   sortByDateDesc,
   splitRacesByDate,
 } from "./raceMetrics";
+
+export { buildMonthCells, groupRacesByYmd, toYmd, WEEKDAY_LABELS_SHORT_RU } from "./calendarUtils";