Update lib.rs

[kimcascante]

Summary

Enforces zero warnings in contracts crate using #![deny(warnings)] and CI checks.

Closes #162

Changes

• Added #![deny(warnings)] to contract crate
• Fixed all Clippy warnings
• Updated CI to fail on warnings
• Updated README with lint instructions

Testing

• cargo test ✔
• cargo clippy ✔
• Coverage ≥ 95%

Security Notes

• No logic changes
• No storage changes
• Compile-time enforcement only

[drips-wave]

@kimcascante Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

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