Add support for recurring calendar events

[vuanj]

Adds support for creating recurring calendar events in the ekctl command-line tool, along with options for recurrence rules, improved event output, and updated documentation.

Recurring event support and options

• Added new options to the ekctl add event command for recurrence:
  • --frequency
  • --interval
  • --days-of-the-week
  • --days-of-the-month
  • --months-of-the-year
  • --weeks-of-the-year
  • --days-of-the-year
  • --set-positions
  • --recurrence-end-date
  • --recurrence-count
• Implemented parsing and validation for recurrence options, including ISO8601 date handling, day-of-week parsing (e.g., 1mon, -1fri), and interval/count/end date logic.

EventKit integration and logic

• Updated EventKitManager to build and attach an EKRecurrenceRule to events, including logic to adjust event start dates for complex monthly recurrences (e.g., “last Friday of the month”).
• Extended event JSON output to include recurrence rule details for events with recurrence

Documentation and versioning

• Updated the README.md to document recurring event support, including usage examples and a table explaining recurrence options.
• Bumped the tool version to 1.3.0 to reflect the new feature.

Test and authoring

• Tested on MacOS Tahoe 26.4.1
• A Claude Code agent was used to write this code based on Apple's Swift documentation