Hardcoded Payout Ratio in claim_winnings

[hman38705]

Description
claim_winnings (Line 140) contains a simplified placeholder: let winnings = bet.amount;. This completely breaks the parimutuel nature of the platform, as winners only receive their initial stake back rather than a share of the total pool. It also results in the contract accumulating stuck funds from losing bets with no way to distribute them.

Requirements and context

• Implement the parimutuel payout formula: (bet_amount / winning_outcome_stake) * total_net_pool.
• Ensure all funds from losing bets are correctly distributed to winners.

Suggested execution

• Fork the repo and create a branch: git checkout -b fix/issue-91-parimutuel-distribution
• Implement the weighted payout logic.

Implementation changes

• Modify bets.rs (Line 140) to calculate the proportional share of the market pool.

Test and commit

• Verify that if 10 users bet 100 XLM each and 2 win, each winner receives 500 XLM.

Example commit message
fix: implement real parimutuel payout calculation in claim_winnings

Guidelines

• Economic model correctness.
• Timeframe: 48 hours.

[oncleweynom]

@oncleweynom has applied to work on this issue as part of the Stellar Wave Program's 3rd wave.

i would love to work on this issues maintainer

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