test(11-05): RED — CR-01 custom alarm round-trip

- expand.test.ts: 3 new tests asserting reminderIsCustom:true for
  absolute DATE-TIME trigger and multi-VALARM, false for relative preset
- EventForm.test.tsx: 3 new tests asserting __custom__ picker init,
  'Custom (kept)' option visibility, and payload omits reminderLeadMinutes
- Fixtures: absolute-alarm.ics (DATE-TIME VALARM), multi-alarm.ics (2 VALARMs)
- All 6 new tests FAIL (RED): reminderIsCustom field not yet on interface

apps/api/tests/fixtures/absolute-alarm.ics

@@ -0,0 +1,14 @@
+BEGIN:VCALENDAR
+VERSION:2.0
+PRODID:-//Apple Calendar//NONSGML Version 1//EN
+BEGIN:VEVENT
+UID:absolute-alarm-test@familysync.test
+DTSTART;VALUE=DATE:20261215
+SUMMARY:Holiday Party
+BEGIN:VALARM
+ACTION:DISPLAY
+DESCRIPTION:Reminder
+TRIGGER;VALUE=DATE-TIME:20261214T140000Z
+END:VALARM
+END:VEVENT
+END:VCALENDAR