[P2] Add links in event description

[KalebCole]

Priority: P2 (Medium)

Add clickable links in event description.

Current State

--description exists but unclear if links render correctly.

Requirements

partiful create --title "Watch Party" \
  --description "Join us for the game!\n\nStream: https://twitch.tv/example"

# Or with explicit link flag
partiful create --title "Meetup" \
  --link "https://zoom.us/j/123456" \
  --link-text "Zoom Link"

Implementation Notes

• Test if raw URLs in description become clickable
• If not, find the proper field for links (Partiful may have dedicated link field)
• May need to use --links array in API payload

Acceptance Criteria

• URLs in description are clickable on Partiful
• Dedicated --link option if Partiful has link field
• Multiple links supported