feat(02-03): hydrateEvents + calendarStore + windowed fetchEvents; RED stubs green

- Create hydrateEvents.ts: Temporal.PlainDate for allDay, ZonedDateTime for timed
  calendarId routes via isShared ? 'shared' : String(ownerUserId) — NOT String(calendarId)
  _familySync carries uid/color/isShared through to popover
- Update hydrateEvents.test.ts: add temporal-polyfill/global import; all 4 RED stubs now GREEN
- Create calendarStore.ts: Zustand store with selectedView (localStorage per breakpoint group),
  selectedDate, openEventId, calendarRange; D-05 view defaults; calendarRange ± buffer for
  initial TanStack Query key without depending on onRangeUpdate firing on mount
- Update client.ts: add CalendarOccurrence/OccurrencesResponse, windowed fetchEvents(start,end)
  with credentials:include; keep legacy CalendarEvent/EventsResponse + fetchEventsLegacy
  as deprecated for EventProof.tsx (removed in Plan 05)
- Update EventProof.tsx: switch to fetchEventsLegacy to keep build clean until Plan 05
- tsc --noEmit clean; all 18 PWA tests pass

apps/pwa/src/lib/hydrateEvents.test.ts

@@ -14,9 +14,9 @@
  *     This assertion locks the Plan 03 routing fix.
  */
 
+import 'temporal-polyfill/global'
 import { describe, it, expect } from 'vitest'
 
-// Not yet built — import will fail (RED state) until Plan 03 implements hydrateEvents.ts
 import { hydrateEvents } from './hydrateEvents.js'
 
 // Minimal CalendarOccurrence shape for test purposes