Remove unused dependencies; tidy imports and minor cleanups

[arividar]

Summary

There are unused dependencies and small import cleanups that will simplify the codebase and reduce build surface.

Observations

• fs = "0.0" appears unused in the code.
• rand appears unused in the library/binary.
• Duplicate import in src/main.rs: use std::fs::read_dir; appears twice.

Tasks

• Remove unused crates from Cargo.toml (e.g., fs, rand) if confirmed unused.
• Run cargo check to verify no usages remain; adjust code if needed.
• Remove duplicate/unused use statements (e.g., duplicate read_dir).
• Optionally run cargo clippy -- -D warnings and fix warnings.
• Ensure cargo fmt clean formatting.

Acceptance criteria

• cargo check and cargo test pass.
• No unused dependency warnings; imports are tidy.
• CI/build remains green.