[design] Book-cover style story cards on home page

[realproject7]

Overview

Redesign the story grid cards on the home page to look like book covers. This is an experimental design change — must be easily revertible.

Requirements

1. Book-shaped card (inside the box)

• Extend vertical height to a portrait/book aspect ratio (roughly 2:3)
• Keep the existing simple outline border style — no gradients, no shadows, no 3D effects
• Dark background consistent with current design tokens

2. Book cover content (inside the box)

• Title — prominent, upper area of the card
• Genre — subtle, mid or upper area (smaller text or tag style)
• Author name — bottom area of the card (resolve Farcaster identity where available)
• Typography should feel like a real book cover — clean hierarchy, well-spaced

3. Metadata row (outside/below the box)

• TVL (token value locked)
• Number of plots
• Rating
• Compact, single row, clean alignment — no clutter

4. Responsive grid

• Desktop: 3 columns (same as current)
• Mobile: 2 columns (currently 1) — cards should still be readable at this size

Files to modify

• src/components/StoryCard.tsx — main card component
• src/app/page.tsx — grid layout (responsive columns)
• src/app/globals.css — if new design tokens needed

Design reference

Use the attached screenshot as directional reference for the book shape and content placement. Do NOT replicate the gradient or 3D spine effect — keep PlotLink's existing flat outline aesthetic.

Revert instructions

IMPORTANT: This is an experimental design change.

1. Before starting, create a git tag on main: git tag pre-book-cards
2. All changes must go in a single PR
3. If the operator requests a revert after merge: git revert <merge-commit-hash> to cleanly undo

Acceptance criteria

• Cards are portrait/book-shaped with outline border
• Title, genre, author displayed inside the card like a book cover
• TVL, plot count, rating displayed below the card
• Desktop: 3-column grid
• Mobile: 2-column grid
• Existing dark theme + monospace font preserved
• npm run typecheck passes
• Single PR for easy revert