feat(06-06): add whole-series edit confirmation prompt

- Create SeriesEditPrompt.tsx: bottom-sheet (phone) / dialog (desktop) matching
  DeleteConfirmationDialog pattern; focus trap, Escape=cancel, role=dialog/aria-modal
- UI-SPEC Surface 6 copy: 'Edit recurring series' heading, 'This will update all
  occurrences of this event.' body, 'Update series' accent-filled CTA, 'Cancel' ghost
- Import SeriesEditPrompt + add seriesEditPromptOpen state to EventForm
- handleSubmit gates on occurrence.hasRrule: opens prompt for recurring edits;
  executeSubmit() fires the existing whole-series PATCH on confirmation
- Save CTA label becomes 'Update series' for recurring edits (UI-SPEC primary CTAs)
- Non-recurring and create-mode Save behavior unchanged (no prompt)

apps/pwa/src/components/EventForm.tsx

@@ -45,6 +45,7 @@ import {
   computeNewTimedEnd,
   computeNewAllDayEnd,
 } from '../lib/eventDateTime.js'
+import { SeriesEditPrompt } from './SeriesEditPrompt.js'
 
 // ── Constants ─────────────────────────────────────────────────────────────────
 
@@ -276,6 +277,8 @@ export function EventForm() {
   // ── Validation state ────────────────────────────────────────────────────────
 
   const [errors, setErrors] = useState<{ title?: string; endTime?: string; recurrenceBound?: string }>({})
+  // D-08/D-09: series-edit confirmation prompt state
+  const [seriesEditPromptOpen, setSeriesEditPromptOpen] = useState(false)
 
   // ── Mutations ───────────────────────────────────────────────────────────────
 
@@ -360,9 +363,13 @@ export function EventForm() {
     return Object.keys(newErrors).length === 0
   }
 
-  const handleSubmit = () => {
-    if (!validate()) return
-
+  /**
+   * Build the payload and fire the mutation. Called directly for non-recurring edits
+   * and create mode; called from the SeriesEditPrompt onConfirm for recurring edits
+   * (D-08/D-09). The whole-series PATCH reuses the existing /api/events/:uid/edit route
+   * which PUTs the master VEVENT — no RECURRENCE-ID, per D-08.
+   */
+  const executeSubmit = () => {
     // BUG A fix: serialize timed events to an unambiguous UTC instant here in
     // the browser (operator's zone is known) instead of sending a naive local
     // wall-clock string. The API container is UTC; a naive string was being read
@@ -403,6 +410,20 @@ export function EventForm() {
     mutation.mutate(payload)
   }
 
+  const handleSubmit = () => {
+    if (!validate()) return
+
+    const isEdit = eventFormMode === 'edit' && !!eventFormUid
+
+    // D-08/D-09: gate recurring-series edits behind the confirmation prompt
+    if (isEdit && occurrence?.hasRrule === true) {
+      setSeriesEditPromptOpen(true)
+      return
+    }
+
+    executeSubmit()
+  }
+
   // ── Keyboard: Escape to close ───────────────────────────────────────────────
 
   useEffect(() => {
@@ -466,11 +487,15 @@ export function EventForm() {
 
   const isPhone = isPhoneBreakpoint()
   const label = eventFormMode === 'edit' ? 'Edit Event' : 'New Event'
+  // D-08/D-09: CTA label is "Update series" for recurring edits (UI-SPEC "EventForm primary CTAs")
+  const isEditRecurring = eventFormMode === 'edit' && occurrence?.hasRrule === true
   const saveLabel = mutation.isPending
     ? 'Saving…'
-    : eventFormMode === 'edit'
-      ? 'Save Changes'
-      : 'Create Event'
+    : isEditRecurring
+      ? 'Update series'
+      : eventFormMode === 'edit'
+        ? 'Save Changes'
+        : 'Create Event'
 
   const dialogStyle: React.CSSProperties = isPhone
     ? {
@@ -1014,6 +1039,16 @@ export function EventForm() {
           </button>
         </div>
       </div>
+
+      {/* D-08/D-09: Series-edit confirmation prompt — shown when editing a recurring occurrence */}
+      <SeriesEditPrompt
+        open={seriesEditPromptOpen}
+        onConfirm={() => {
+          setSeriesEditPromptOpen(false)
+          executeSubmit()
+        }}
+        onCancel={() => setSeriesEditPromptOpen(false)}
+      />
     </>
   )
 }