feat: add gas optimization tooling and reporting in Makefile

[2PykeETH]

Summary

This PR introduces a gas optimization section in the Makefile, enabling developers to track, compare, and analyze gas consumption across the project.

---

Changes

• New Makefile Tasks

  • gas-snapshot → create a gas usage snapshot
  • gas-diff → compare current gas usage against snapshot
  • gas-report → generate a detailed gas usage report and save to reports/gas-report.txt

• Documentation

  • Added NatSpec-style section header for gas optimization

---

Benefits

• Provides visibility into gas usage trends
• Enables developers to detect regressions in gas costs early
• Produces a detailed gas cost report for optimization analysis

---

Next Steps

• Integrate gas snapshot checks into CI/CD pipeline
• Add thresholds for acceptable gas diffs to enforce optimization goals
• Explore per-function gas profiling for more granular insights