feat: implement Reputation Engine for TruthBounty V2

[Handynfts2]

• Add ReputationEngine contract with reputation registry and storage structure
• Implement reputation initialization (standard and custom with UPDATE_ROLE)
• Add reputation retrieval APIs (getReputation, getReputationScore, reputationExists)
• Implement reputation weight calculation with 10x cap
• Add protocol-wide and per-verifier statistics tracking
• Implement verification recording functions (successful, failed, disputed)
• Add reward recording and batch update functions
• Include comprehensive event emissions for reputation lifecycle
• Add role-based access control (ADMIN, UPDATE, PAUSER)
• Implement governance integration for parameter updates
• Add pause functionality for emergency situations
• Include upgrade-safe storage layout with gap
• Add MockGovernanceController for testing
• Create comprehensive unit tests (60+ test cases)
• Create fuzz tests for edge cases and determinism
• Create integration tests with staking and governance
• Add detailed documentation with gas benchmarks

closes #287