Formatting, Linting & Pre-commit Hooks

[ahmadogo]

Description:

Enforce code quality locally with rustfmt, clippy, and optional pre-commit hooks.

Tasks:

• Add rustfmt.toml (project style)
• Ensure cargo clippy has deny rules for common pitfalls
• Configure optional pre-commit hooks (fmt, clippy, cargo test)
• Document usage in CONTRIBUTING

Acceptance Criteria:

• cargo fmt --all changes nothing on clean repo
• Clippy runs with strict settings; no warnings in main
• Pre-commit (optional) works for contributors who enable it