Add MarketAnalytics top-N participants leaderboard with bounded heap

[greatest0fallt1me]

Description

market_analytics.rs exposes aggregate stats but no leaderboard. Add a top-N participants query backed by a bounded heap (default N=10) maintained incrementally on every place_bet so reads are O(N) regardless of total participant count.

Requirements and Context

• Heap stored under DataKey::MarketLeaderboard(market_id)
• Insert is O(log N); N capped at 50 via config
• View function returns sorted descending by stake
• Must be secure, tested, and documented
• Should be efficient and easy to review

Suggested Execution

1. Fork the repo and create a branch

   git checkout -b feature/leaderboard-bounded-heap

2. Implement changes
   • contracts/predictify-hybrid/src/market_analytics.rs
   • contracts/predictify-hybrid/src/bets.rs
3. Test and commit
   • cargo test -p predictify-hybrid leaderboard
   • Cover edge cases
   • Include test output and notes in the PR

Example commit message

feat: maintain bounded top-N leaderboard in MarketAnalytics

Acceptance Criteria

• Heap size never exceeds N
• Reads return entries sorted descending
• Updates run in O(log N) worst case

Guidelines

• No unwrap() in production paths
• Clear documentation and inline comments
• Timeframe: 96 hours

[Ayomide-codex]

@Ayomide-codex has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Would love to work on this. Kindly assign to me. Please

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Ayomide-codex to this issue.

[drips-wave]

Congratulations, @Ayomide-codex! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

🧑‍💻 @Ayomide-codex: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

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