Fix compilation error and clean up connection.rs for better reliability

[nafisatou]

This issue addresses a compilation error in connection.rs due to Rust not inferring the type of result. It also cleans up minor warnings and improves error handling.

Changes

• Added type annotation: let result: anyhow::Result<()>
• Replaced Err(format!(...)) with anyhow::bail!
• Removed unused mut and silenced warnings
• Added short doc comments for clarity