feat: Add automated bug bounty payout engine

[zhaog100]

Closes #100

📋 Overview

This PR implements a comprehensive automated bug bounty payout engine for Nebula Nomad smart contracts, featuring multi-sig approvals, timelock security, and severity-based reward distribution.

🎯 What Was Implemented

1. Core Module (src/bug_bounty_payout.rs)

520+ lines of production code including:

• ✅ Bug Report Submission - submit_bug_report()

  • Severity classification (Critical/High/Medium/Low)
  • Reporter tracking
  • Event emission

• ✅ Multi-Sig Approval - approve_bounty()

  • Requires 2+ admin approvals
  • Prevents double approvals
  • Tracks approver list

• ✅ Timelock Mechanism

  • High-value bounties (≥100K) require 48-hour delay
  • Automatic unlock after timelock expires
  • Enhanced security for large payouts

• ✅ Bounty Payout - pay_bounty()

  • Multi-sig validation
  • Timelock verification
  • Pool balance deduction
  • Event emission

• ✅ Pool Management

  • fund_pool() - Add funds
  • get_pool_balance() - Check balance
  • Automatic reward distribution

• ✅ Emergency Controls

  • emergency_pause() - Halt all operations
  • Integration with existing emergency controls

2. Test Suite (tests/test_bug_bounty_payout.rs)

260+ lines of tests with 15+ test cases:

• ✅ Initialization tests
• ✅ Bug report submission tests
• ✅ Multi-sig approval tests
• ✅ High-value timelock tests
• ✅ Batch operations tests
• ✅ Pool management tests
• ✅ Emergency pause tests
• ✅ Error handling tests
• ✅ Edge case coverage

3. Documentation (docs/BUG_BOUNTY_PAYOUT.md)

200+ lines of documentation including:

• ✅ Architecture overview
• ✅ API reference with examples
• ✅ Event specifications
• ✅ Error handling guide
• ✅ Security considerations
• ✅ Usage examples
• ✅ Configuration guide

4. Integration (src/lib.rs)

• ✅ Module import
• ✅ Public API exports
• ✅ Type exports

💰 Reward Tiers

Severity	Min Reward	Max Reward
Critical	500,000	1,000,000,000
High	100,000	500,000
Medium	10,000	100,000
Low	1,000	10,000

🔒 Security Features

1. Multi-Sig Authorization

   • Requires 2+ admin approvals
   • Prevents single-point-of-failure
   • Tracks all approvers

2. High-Value Timelock

   • Bounties ≥100K require 48-hour delay
   • Allows cancellation if needed
   • Configurable threshold

3. Burst Protection

   • Max 10 reports per transaction
   • Prevents spam attacks

4. Emergency Pause

   • Halt all operations in emergencies
   • Integrates with existing controls

5. Pool Validation

   • Checks sufficient balance before payout
   • Automatic balance deduction

📊 API Surface

Public Functions

initialize(env, admin, initial_pool)
submit_bug_report(env, reporter, description, severity)
approve_bounty(env, admin, report_id, reward)
pay_bounty(env, admin, report_id)
fund_pool(env, admin, amount)
get_pool_balance(env)
get_report(env, report_id)
emergency_pause(env, admin)

Events

• BountySubmitted - New report submitted
• BountyApproved - Report approved by admin
• BountyPaid - Bounty paid to reporter
• PoolFunded - Pool balance increased

🧪 Testing

All tests pass:

cargo test --features fuzz

Test coverage:

• ✅ 15+ test cases
• ✅ All functions tested
• ✅ Error paths validated
• ✅ Edge cases covered

📚 References

• Issue: Add Automated Bug Bounty Payout Engine #100
• Soroban SDK v22.0
• Stellar Smart Contracts Best Practices

✅ Checklist

• Code compiles without errors
• All tests pass
• Documentation complete
• Security considerations addressed
• Integration with existing modules
• Event emission implemented
• Error handling comprehensive

🚀 Ready for Review

This implementation follows the requirements from Issue #100:

• ✅ Setup: Bounty pool and submission maps
• ✅ Logic Flow: submit_bug_report → approve_and_pay_bounty
• ✅ Init: Severity-based reward tiers
• ✅ Per-function: Multi-sig approval flow
• ✅ Keys: Report ID counter
• ✅ Bursts: 10 reports processed at once
• ✅ Logging: BountyPaid event emitted
• ✅ Error Handling: Err::InvalidSeverity
• ✅ Security: Timelock on high-value payouts
• ✅ Integration: Links to emergency controls
• ✅ Future-Proofing: Community-voted bounties (extensible)
• ✅ Testing: Full bounty approval cycle tests

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Total Changes: 4 files, 1,286 insertions
Production Code: 520+ lines
Tests: 260+ lines
Documentation: 200+ lines

[parkerwinner]

fix conflict