🔐 Guardian Contract Security Enhancements:
- Add persistent SQLite storage for spending history and pending operations
- Replace in-memory state with database-backed state management
- Implement _init_storage(), _load_state(), _save_state() for state persistence
- Add _load_spending_history(), _save_spending_record() for transaction tracking
- Add _load_pending_operations(), _save_pending_operation(), _remove_pending_operation()
- Change file mode from 644 to 755 for all project files
- Add chain_id parameter to get_balance RPC endpoint with default "ait-devnet"
- Rename Miner.extra_meta_data to extra_metadata for consistency
