feat(03-06): add deleteEvent, fetchSyncStatus client calls and delete/sync Zustand keys

- deleteEvent(uid): DELETE /api/events/:uid with credentials:include, throws on !ok
- fetchSyncStatus(uid): GET /api/events/sync-status?uid= returning SyncStatus
- Export SyncStatus and SyncStatusValue types
- Zustand: deleteDialogOpen/deleteDialogUid/lastSyncedUid keys + setDeleteDialog/setLastSyncedUid setters

apps/pwa/src/store/calendarStore.ts

@@ -43,6 +43,13 @@ export interface CalendarStore {
   eventFormMode: 'create' | 'edit'
   eventFormUid: string | null
 
+  // ── Delete dialog + sync-state UI state (Plan 03-06) ─────────────────────
+  // Drives DeleteConfirmationDialog visibility and SyncStateToast polling.
+  deleteDialogOpen: boolean
+  deleteDialogUid: string | null
+  /** UID of the most recently enqueued write. SyncStateToast polls sync-status for this. */
+  lastSyncedUid: string | null
+
   setSelectedView: (view: string) => void
   setSelectedDate: (date: string) => void
   setOpenEventId: (id: string | null) => void
@@ -56,6 +63,20 @@ export interface CalendarStore {
    * @param uid    UID of the event to pre-populate in edit mode (null otherwise)
    */
   setEventForm: (open: boolean, mode?: 'create' | 'edit', uid?: string | null) => void
+
+  /**
+   * Open or close the DeleteConfirmationDialog.
+   *
+   * @param open true to open, false to close
+   * @param uid  UID of the event to confirm-delete (null when closing)
+   */
+  setDeleteDialog: (open: boolean, uid?: string | null) => void
+
+  /**
+   * Set the UID of the most recently enqueued write, driving SyncStateToast polling.
+   * Pass null to dismiss the toast.
+   */
+  setLastSyncedUid: (uid: string | null) => void
 }
 
 // ── Helpers ────────────────────────────────────────────────────────────────
@@ -115,6 +136,11 @@ export const useCalendarStore = create<CalendarStore>((set) => ({
   eventFormMode: 'create',
   eventFormUid: null,
 
+  // Delete dialog + sync-state UI state — closed/null by default
+  deleteDialogOpen: false,
+  deleteDialogUid: null,
+  lastSyncedUid: null,
+
   setSelectedView: (view: string) => {
     set({ selectedView: view })
     // Persist to localStorage keyed by breakpoint group
@@ -135,4 +161,9 @@ export const useCalendarStore = create<CalendarStore>((set) => ({
 
   setEventForm: (open: boolean, mode: 'create' | 'edit' = 'create', uid: string | null = null) =>
     set({ eventFormOpen: open, eventFormMode: mode, eventFormUid: uid }),
+
+  setDeleteDialog: (open: boolean, uid: string | null = null) =>
+    set({ deleteDialogOpen: open, deleteDialogUid: uid }),
+
+  setLastSyncedUid: (uid: string | null) => set({ lastSyncedUid: uid }),
 }))