- Add parentId column to wishlist_comments for reply threading
- Create wishlist_comment_votes table for up/down voting
- Add deleteComment action (owner-only, cascades to replies)
- Add toggleCommentVote action with toggle behavior
- Update getItemWithComments to return nested CommentWithMeta
- Create CommentItem component with voting UI and reply support
- One level of reply depth enforced (can't reply to replies)
