[P2] Clone/duplicate events

[KalebCole]

Priority: P2 (Medium) Quickly duplicate an existing event with a new date. ## Use Cases - Copy last weeks game night for this week - Clone successful event format - Faster than templates for one-off copies ## Proposed Commands bash # Clone event with new date partiful clone <eventId> --date "Apr 22 7pm" # Clone and modify partiful clone <eventId> --date "Apr 22 7pm" --title "Game Night Vol 2" # Clone without guests (fresh start) partiful clone <eventId> --date "Apr 22 7pm" --no-guests # Clone with same guests pre-invited partiful clone <eventId> --date "Apr 22 7pm" --reinvite going ## What Gets Copied - Title, description, location - Capacity and waitlist settings - Image/poster - Display settings (theme, etc) ## What Does NOT Get Copied - Guests/RSVPs (unless --reinvite) - Comments/activity - Messages ## Acceptance Criteria - [ ] Clone event with new date - [ ] Option to modify fields during clone - [ ] Option to reinvite previous guests - [ ] Clear output showing what was copied