feat(03-02): implement buildVeventString VEVENT builder (Task 1 GREEN)
- buildVeventString(NewEventParams) → { uid, icsString } using ical.js ICAL.Component
- All-day events use ICAL.Time({ isDate: true }) → VALUE=DATE, no TZID, no time (D-13)
- Timed events use ICAL.Time.fromJSDate(date, true) → DTSTART:...Z, no TZID (D-13)
- RRULE serialized via ICAL.Recur.fromString + ICAL.Property (prevents char-split bug)
- Exports: buildVeventString, NewEventParams, RRULE_PRESETS (daily/weekly/monthly/yearly)
- Uses crypto.randomUUID() for UID generation; appends @familysync suffix
- All 7 vevent.test.ts assertions GREEN
Lucas Berger
b23b9597df