feat(contracts): implement gas optimization audit and fix top-10 gas consumers

[cypriannwokolo2-creator]

Summary

Gas usage has not been systematically optimized. The top-10 gas-consuming functions should be profiled and optimized.

Acceptance Criteria

• Profile gas usage for all public functions
• Identify top-10 gas consumers
• Optimize: reduce storage reads, batch operations, use instance storage
• Document gas improvements
• Ensure all functions within AGENTS.md gas budgets

Complexity

High.