fix: implement real parimutuel payout calculation in claim_winnings

[oncleweynom]

Closes #194

• Deduct protocol fee (calculate_tiered_fee) at bet placement time
• Store net (post-fee) amount in bet.amount, total_staked, outcome_stakes
• Parimutuel formula: winnings = (bet.amount * total_staked) / winning_outcome_stake
• Fees are collected via collect_fee and withdrawable by admin
• Referral rewards computed from actual fee charged
• Resolve OracleConfig duplicate fields in types.rs
• Add winner_counts and total_claimed fields to Market struct
• Fix lib.rs: remove duplicate/broken function definitions, simplify initialize signature
• Fix merge-conflict artifacts in bets_test.rs, test.rs, common/mod.rs
• Fix integration_test.rs and lifecycle_test.rs call signatures
• Update all affected test assertions to reflect net amounts

Fixes #91 winners now receive proportional share of the net pool. Example: 10 users bet 100 XLM each, 2 win -> each receives 500 XLM (0% fee).

Pull Request

📋 Description

Brief description of the changes in this PR.

🎯 Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Performance improvement
• Code refactoring
• Test addition/update
• CI/CD update

🔗 Related Issues

Closes #(issue number)
Relates to #(issue number)

📝 Changes Made

• Change 1
• Change 2
• Change 3

🧪 Testing

Test Coverage

• Unit tests added/updated
• Integration tests added/updated
• All tests passing locally
• Test coverage maintained/improved

Manual Testing

• Tested on testnet
• Tested locally
• Edge cases tested

Test Results:

[Paste test output or describe manual testing performed]

📸 Screenshots (if applicable)

[Add screenshots for UI changes]

✅ Checklist

Code Quality

• Code follows project style guidelines
• Self-review completed
• Comments added for complex code
• No unnecessary console.log or debug code
• No commented-out code

Documentation

• Documentation updated (if needed)
• API documentation updated (if applicable)
• CHANGELOG.md updated
• README updated (if needed)

Testing & Quality

• All tests pass (cargo test)
• No linting errors (cargo clippy)
• Code formatted (cargo fmt)
• No new warnings introduced
• Gas benchmarks run (if applicable)

Security

• Security implications considered
• No sensitive data exposed
• Input validation added
• Authorization checks in place

Git

• Branch is up to date with main
• Commits are atomic and well-described
• Commit messages follow convention
• No merge conflicts

🔍 Reviewer Notes

[Any specific areas you'd like reviewers to focus on]

📊 Performance Impact

• No performance impact
• Performance improved
• Performance impact acceptable (explain below)

Details:
[Describe any performance implications]

🚀 Deployment Notes

[Any special deployment considerations, migration steps, or configuration changes needed]

📚 Additional Context

[Add any other context about the PR here]

---

By submitting this PR, I confirm that:

• I have read and followed the CONTRIBUTING.md guidelines
• My code follows the project's coding standards
• I have tested my changes thoroughly
• I am ready for code review

[drips-wave]

@oncleweynom Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

Learn more about application limits