feat(03-06): wire EventDetailPopover Edit/Delete footer and implement DeleteConfirmationDialog

- EventDetailPopover: replace aria-hidden placeholder with Edit2/Trash2 footer buttons
  - Edit opens EventForm in edit mode and closes popover
  - Delete opens DeleteConfirmationDialog via setDeleteDialog (T-03-17 two-tap)
- DeleteConfirmationDialog: centered modal, max-width 320px, backdrop + focus trap
  - heading 'Delete event?', Fastmail body copy per UI-SPEC
  - Cancel/Escape close without deleting; Delete fires mutation
  - On success: setLastSyncedUid (feeds SyncStateToast), close dialog + popover
  - TanStack mutation; 48px Delete button (--color-destructive)
- CalendarShell: mount DeleteConfirmationDialog in both phone and tablet/desktop layouts

apps/pwa/src/components/CalendarShell.tsx

@@ -47,6 +47,7 @@ import { buildCalendarConfig, SX_FIRST_DAY_OF_WEEK } from '../lib/calendarConfig
 import { useCalendarStore } from '../store/calendarStore.js'
 import { EventDetailPopover } from './EventDetailPopover.js'
 import { EventForm } from './EventForm.js'
+import { DeleteConfirmationDialog } from './DeleteConfirmationDialog.js'
 import { SyncStateToast } from './SyncStateToast.js'
 import { AppNav } from './AppNav.js'
 import { ColorLegend } from './ColorLegend.js'
@@ -355,6 +356,9 @@ export function CalendarShell() {
         {/* EventForm modal — conditionally rendered while eventFormOpen */}
         {eventFormOpen && <EventForm />}
 
+        {/* DeleteConfirmationDialog — always mounted; renders nothing when deleteDialogOpen is false */}
+        <DeleteConfirmationDialog />
+
         {/* SyncStateToast — always mounted; renders nothing when lastSyncedUid is null */}
         <SyncStateToast />
       </div>
@@ -429,6 +433,9 @@ export function CalendarShell() {
       {/* EventForm modal — conditionally rendered while eventFormOpen */}
       {eventFormOpen && <EventForm />}
 
+      {/* DeleteConfirmationDialog — always mounted; renders nothing when deleteDialogOpen is false */}
+      <DeleteConfirmationDialog />
+
       {/* SyncStateToast — always mounted; renders nothing when lastSyncedUid is null */}
       <SyncStateToast />
     </div>