fix(multicall): resolve critical multicall parsing corruption issues

- Added comprehensive bounds checking to prevent buffer overruns in multicall parsing
- Implemented graduated validation system (Strict/Moderate/Permissive) to reduce false positives
- Added LRU caching system for address validation with 10-minute TTL
- Enhanced ABI decoder with missing Universal Router and Arbitrum-specific DEX signatures
- Fixed duplicate function declarations and import conflicts across multiple files
- Added error recovery mechanisms with multiple fallback strategies
- Updated tests to handle new validation behavior for suspicious addresses
- Fixed parser test expectations for improved validation system
- Applied gofmt formatting fixes to ensure code style compliance
- Fixed mutex copying issues in monitoring package by introducing MetricsSnapshot
- Resolved critical security vulnerabilities in heuristic address extraction
- Progress: Updated TODO audit from 10% to 35% complete

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

docs/SECURITY_AUDIT_REPORT.md

@@ -56,8 +56,8 @@ func safeUint32(val uint64) (uint32, error) {
 **Finding:** RPC endpoints hardcoded in source:
 ```go
 // pkg/arbitrage/service.go:994-995
-RPCEndpoint: "wss://arbitrum-mainnet.core.chainstack.com/f69d14406bc00700da9b936504e1a870",
-WSEndpoint:  "wss://arbitrum-mainnet.core.chainstack.com/f69d14406bc00700da9b936504e1a870",
+RPCEndpoint: "wss://arbitrum-mainnet.core.chainstack.com/53c30e7a941160679fdcc396c894fc57",
+WSEndpoint:  "wss://arbitrum-mainnet.core.chainstack.com/53c30e7a941160679fdcc396c894fc57",
 ```
 
 **Risk:**