[Airdrop] Redesign /airdrop page with 2-column grid layout

[realproject7]

Parent: #877

Problem

The current /airdrop page stacks all sections vertically. It should use a 2-column grid layout matching the story detail page (/story/[id]).

Solution

Below the hero section, use the same 2-column grid as the story page:

• Left column (wider): User-specific sections — points breakdown, streak card, referral link, "Who referred you?" input
• Right column (narrower): Global sections — leaderboard, weekly snapshots, milestone progress

On mobile, columns stack vertically (left on top, right below).

Reference

See /story/[storylineId] page layout — left column has story content, right column has Price History + Trade to Support. Same proportions and responsive behavior.

Files

• src/app/airdrop/page.tsx — restructure layout to 2-column grid
• src/components/airdrop/UserPoints.tsx — left column
• src/components/airdrop/StreakCard.tsx — left column
• src/components/airdrop/Leaderboard.tsx — right column
• src/components/airdrop/WeeklySnapshots.tsx — right column

Acceptance Criteria

• 2-column grid below hero (matching story page proportions)
• Left: user points, streak, referral
• Right: leaderboard, weekly snapshots
• Responsive: stacks on mobile