fix(02): show owner name / Family in event popover footer

Backend:
- expand.ts: add ownerName: string | null to CalendarOccurrence
  interface and expandOccurrences() signature; thread it onto every
  emitted occurrence.
- events.ts: SELECT users.displayName as ownerName in the join; pass
  it to expandOccurrences().

Frontend:
- client.ts: add ownerName: string | null to CalendarOccurrence.
- EventDetailPopover.tsx: render isShared ? 'Family' :
  (ownerName ?? calendarName) in the footer instead of calendarName.

Tests:
- expand.test.ts: pass ownerName to all expandOccurrences() calls;
  assert ownerName is carried onto occurrences in the DST test.
- events.test.ts: add ownerName to mock rows; assert ownerName present
  on occurrences; add ownerName assertion to timed-recurring test.
- EventDetailPopover.test.tsx: add ownerName to fixtures; split
  "calendar name in footer" into three targeted tests covering
  personal-with-owner, shared→Family, and null-owner fallback.

apps/pwa/src/api/client.ts

@@ -57,6 +57,12 @@ export interface CalendarOccurrence {
   calendarId: number    // DB calendar-row id — do NOT use for SX calendarId routing
   calendarName: string
   ownerUserId: number   // DB user id — the correct Schedule-X routing key
+  /**
+   * Display name of the calendar owner (users.displayName from the API).
+   * Null when the user has not configured a display name.
+   * Popover renders: isShared ? 'Family' : (ownerName ?? calendarName)
+   */
+  ownerName: string | null
   color: string         // hex from users.color or shared-family constant
   isShared: boolean     // true → 'shared' slot; false → String(ownerUserId) slot
   title: string