CardLayout: vertical alignment via flex-col

[pglevy]

Summary

CardLayout now uses flex flex-col internally so that children can pin footer content to the bottom using mt-auto. This solves the common pattern of cards in a row with variable content length where footers (buttons, prices, actions) should align at the same vertical position.

Changes

• CardLayout.tsx: Added flex flex-col to the outer card div and flex-1 flex flex-col to the inner content wrapper
• Card.stories.tsx: Added VerticalAlignment story showing food-menu and pricing-card patterns

Usage

<div className="grid grid-cols-3 gap-4">
  <CardLayout padding="STANDARD" showBorder={true}>
    <h3>Title</h3>
    <p>Variable length content...</p>
    <div className="mt-auto pt-4">
      <button>Action</button>
    </div>
  </CardLayout>
</div>

No new props needed. For AUTO-height cards (default), this has zero visual effect.

Closes #110