[P9-5] Per-plot comment system with pagination

[realproject7]

Overview

Add a comment section to each genesis and plot page, similar to Wattpad chapter comments.

Components

CommentSection component

• Text input with "Write a comment..." placeholder
• Submit requires connected wallet (sign message for auth, NOT a tx)
• Comment list with pagination (20 per page, "Show more" button)
• Each comment shows: commenter address (truncated), content, timestamp
• Newest first ordering

API routes

• GET /api/comments?storylineId=X&plotIndex=Y&page=1&limit=20
  • Returns paginated comments
  • Include total count for pagination
• POST /api/comments
  • Body: { storylineId, plotIndex, content, signature }
  • Verify wallet signature server-side
  • Rate limit: max 1 comment per address per plot per minute

Where it appears

• Genesis page (main story page): plotIndex = 0
• Each plot detail page: plotIndex = N

Moderation

• Use existing hidden column in comments table
• Admin hide/unhide routes (extend existing moderation pattern from plots)

Acceptance Criteria

• Comment input visible on genesis and each plot page
• Wallet connection required to comment (show CTA if disconnected)
• Comments stored in Supabase comments table
• Pagination with "Show more" (20 per page)
• Comments display: address, content, relative timestamp
• Rate limiting prevents spam
• Hidden comments filtered from display
• Mobile responsive 375px

Blocked by: #185 (DB schema for comments table)

Part of: Phase 9 Epic (#183)