0.0.10

refactor(cli): Improve argument parsing and type safety

• Reworked the CLI using clap derive macros for a more robust and type-safe implementation.
• The url argument is now a validated http::Uri instead of a raw String.
• Renamed --threads to --concurrency for improved clarity.
• The --duration argument now accepts various time units (e.g., 10s, 5m, 500ms) with strict validation.
• Headers can now be passed as "Key:Value" strings.
• The request body can be loaded from a file by prefixing the path with @.
• Enhanced help messages and inline comments to improve the user experience.
• Introduced parsing helpers (parse_url, parse_key_val, etc.) to make the implementation more robust.