feat(03-06): implement SyncStateToast with polled sync-status feedback (D-05/D-06/D-08/D-09)

- SyncStateToast: pending/done/failed/dead states per UI-SPEC
- refetchInterval 3000ms while pending; disabled on terminal status
- done + conflict (412) invalidate ['events'] cache (D-06/D-08)
- done auto-dismisses after 2s; failed/dead persist with dismiss button
- role=status (pending/done) and role=alert (failed/dead) for a11y
- Mounted in CalendarShell (both phone + tablet/desktop layouts)
- EventForm.onSuccess: setLastSyncedUid(uid) instead of invalidateQueries

apps/pwa/src/components/EventForm.test.tsx

@@ -28,11 +28,13 @@ import { QueryClient, QueryClientProvider } from '@tanstack/react-query'
 
 const {
   mockSetEventForm,
+  mockSetLastSyncedUid,
   mockCreateEvent,
   mockUpdateEvent,
   mockFetchWritableCalendars,
 } = vi.hoisted(() => ({
   mockSetEventForm: vi.fn(),
+  mockSetLastSyncedUid: vi.fn(),
   mockCreateEvent: vi.fn().mockResolvedValue({ uid: 'new-uid-123' }),
   mockUpdateEvent: vi.fn().mockResolvedValue({ uid: 'edit-uid-456' }),
   mockFetchWritableCalendars: vi.fn(),
@@ -43,12 +45,18 @@ let mockEventFormMode: 'create' | 'edit' = 'create'
 let mockEventFormUid: string | null = null
 
 vi.mock('../store/calendarStore.js', () => ({
-  useCalendarStore: vi.fn(() => ({
-    eventFormOpen: mockEventFormOpen,
-    eventFormMode: mockEventFormMode,
-    eventFormUid: mockEventFormUid,
-    setEventForm: mockSetEventForm,
-  })),
+  useCalendarStore: vi.fn((selector?: (s: Record<string, unknown>) => unknown) => {
+    const state = {
+      eventFormOpen: mockEventFormOpen,
+      eventFormMode: mockEventFormMode,
+      eventFormUid: mockEventFormUid,
+      setEventForm: mockSetEventForm,
+      setLastSyncedUid: mockSetLastSyncedUid,
+    }
+    // Support both selector form and plain call form
+    if (typeof selector === 'function') return selector(state)
+    return state
+  }),
 }))
 
 vi.mock('../api/client.js', () => ({
@@ -106,12 +114,19 @@ function renderForm(options: {
   mockEventFormOpen = true
   mockEventFormMode = mode
   mockEventFormUid = uid
-  ;(useCalendarStore as unknown as ReturnType<typeof vi.fn>).mockImplementation(() => ({
-    eventFormOpen: true,
-    eventFormMode: mode,
-    eventFormUid: uid,
-    setEventForm: mockSetEventForm,
-  }))
+  ;(useCalendarStore as unknown as ReturnType<typeof vi.fn>).mockImplementation(
+    (selector?: (s: Record<string, unknown>) => unknown) => {
+      const state = {
+        eventFormOpen: true,
+        eventFormMode: mode,
+        eventFormUid: uid,
+        setEventForm: mockSetEventForm,
+        setLastSyncedUid: mockSetLastSyncedUid,
+      }
+      if (typeof selector === 'function') return selector(state)
+      return state
+    },
+  )
 
   mockFetchWritableCalendars.mockResolvedValue(calendars)