Build Leaderboard Module

[Mkalbani]

Description

Implement a leaderboard module that ranks players by score locally and prepares data for on-chain submission.

Acceptance Criteria

• A leaderboard module exists under src/leaderboard/mod.rs
• Leaderboard stores top N scores with player id and timestamp
• New entries replace lower scores when the board is full
• Board is serializable for persistence or on-chain export
• Unit tests cover insertion, replacement, and ranking order

[ayomideadeniran]

I'm a full-stack developer and I'd like to take this issue.
I understand the requirements and will follow the existing project structure, keep the implementation clean, and include proper tests where applicable.

ETA: 1–3 days (depending on scope)
Portfolio: https://knightsdev-portfolio.vercel.app/

[Opulencechuks]

I am confident that i can implement this issue, having worked on similar issues in the past

[grantfox-oss]

🦊 GrantFox — @Opulencechuks has been assigned to this issue as part of the Official Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #18)
2. Your PR will be reviewed by the MindFlowInteractive maintainers

Good luck! Track your progress on GrantFox.