feat(app): set and clear repeat rules on reminders

[baileywickham]

event reads a reminder's recurrenceRules but has no way to write them. This adds repeat-rule flags to reminders create / update, following the LocationOptions pattern:

event reminders create --title "Pay rent" --due "2026-10-01 09:00:00" --recurrence monthly
event reminders update --id <ID> --recurrence weekly --recurrence-interval 2 --recurrence-days mon,wed --recurrence-end 2026-12-31
event reminders update --id <ID> --clear-recurrence

• --recurrence <daily|weekly|monthly|yearly>, refined by --recurrence-interval, --recurrence-end | --recurrence-count, --recurrence-days (names, 3-letter abbreviations or 1–7 with 1 = Sunday), --recurrence-days-of-month, --recurrence-months; --clear-recurrence on update.
• RecurrenceRule.toEKRecurrenceRule() is the inverse of init(from:). A rule on a reminder without a due date fails with a clear message instead of an EventKit save error.
• RecurrenceRule gains an optional occurrenceCount, so count-limited series round-trip through JSON. Defaults to nil; existing call sites and payloads are unaffected.
• macOS-only like location triggers; sync backends untouched.

Tested with swift test (new parsing/validation and EventKit round-trip tests) and against a real Reminders store on macOS 26.

[code-terrier]

Code Terrier Review unavailable for this commit: every reviewer model hit an infrastructure fault (upstream provider unavailable, not a code problem) - push a new commit or @code-terrier review to retry once it clears.