feat(11-04): add reminderLeadMinutes to CreateEventPayload + CalendarOccurrence

- CalendarOccurrence: required reminderLeadMinutes: number | null (atomic mirror of expand.ts, Plan 11-03)
- CreateEventPayload: optional reminderLeadMinutes?: number | null with absent/null/0/positive contract (D-08)
- Update CalendarOccurrence fixtures in EventForm.test.tsx + EventDetailPopover.test.tsx to include the new required field (reminderLeadMinutes: null)
- pwa tsc --noEmit exits 0

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

@@ -59,6 +59,7 @@ const TIMED_OCCURRENCE: CalendarOccurrence = {
   location: 'Conference Room B',
   description: 'Daily team sync meeting',
   hasRrule: false,
+  reminderLeadMinutes: null,
 };
 
 const OCCURRENCE_WITH_HTML: CalendarOccurrence = {
@@ -86,6 +87,7 @@ const ALLDAY_OCCURRENCE: CalendarOccurrence = {
   location: null,
   description: null,
   hasRrule: false,
+  reminderLeadMinutes: null,
 };
 
 // ── Import component (after mocks are declared) ───────────────────────────────

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

@@ -124,6 +124,7 @@ const EDIT_OCCURRENCE: CalendarOccurrence = {
   location: 'Office',
   description: 'Weekly sync',
   hasRrule: false,
+  reminderLeadMinutes: null,
 };
 
 // ── Import component (after mocks) ────────────────────────────────────────────
@@ -506,6 +507,7 @@ const RECURRING_OCCURRENCE: CalendarOccurrence = {
   location: null,
   description: null,
   hasRrule: true,
+  reminderLeadMinutes: null,
   // @ts-expect-error — recurrence is not on CalendarOccurrence type yet; the reset
   // effect reads it if present and defaults to 'none' when absent (WR-03, v1 comment)
   recurrence: 'weekly',
@@ -532,6 +534,7 @@ const LATE_OCCURRENCE: CalendarOccurrence = {
   location: null,
   description: null,
   hasRrule: false,
+  reminderLeadMinutes: null,
 };
 
 describe('EventForm — Plan 03-12 gap closures', () => {
@@ -779,6 +782,7 @@ const ALL_DAY_OCCURRENCE: CalendarOccurrence = {
   location: null,
   description: null,
   hasRrule: false,
+  reminderLeadMinutes: null,
 };
 
 describe('EventForm — Plan 06-06 end-tracking + recurrence-bound', () => {