Global Leaderboard — all-time player rankings

[Empreiteiro]

Description

Add a persistent global leaderboard that tracks cumulative player performance across all battles.

Details

• All-time rankings showing players sorted by total wins, total score, and battles participated
• Stats per player: wins, losses, total score earned, battles played, win rate percentage, highest single-battle score
• Dedicated /leaderboard page accessible from the header nav
• Player profile cards with GitHub avatar, username (linked to GitHub profile), and aggregated stats
• Time filters: all-time, this month, this week
• Storage: aggregate stats in a dedicated Netlify Blob store (leaderboard), updated at the end of each battle

Acceptance Criteria

• New /leaderboard route and page component
• Leaderboard data persisted in Netlify Blobs (not localStorage)
• Updates automatically when a battle finishes
• Responsive layout — table on desktop, cards on mobile
• Avatars link to GitHub profiles