test(02-04): CalendarShell CAL-03 render smoke — Temporal hydration + Pitfall 6 guard

- CalendarShell.test.tsx: 6 tests covering render-without-throw, ScheduleXCalendar mount,
  hydrateEvents called with both timed + all-day occurrences, Temporal.PlainDate guard
  (Pitfall 4/all-day date shift), Temporal.ZonedDateTime for timed (Pitfall 4)
- test-setup.ts: window.matchMedia polyfill for jsdom (calendarStore initialises at module load)
- vitest.config.ts: adds setupFiles pointing to test-setup.ts

apps/pwa/vitest.config.ts

@@ -4,5 +4,6 @@ export default defineConfig({
   test: {
     environment: 'jsdom',
     globals: true,
+    setupFiles: ['./src/test-setup.ts'],
   },
 })