build(release): adopt Rust 2024

[Scott-Nx]

Rust 2024 idioms and code style improvements:

• Updated the Rust edition in Cargo.toml from 2021 to 2024
• Refactored conditional logic throughout the codebase to use the new let-chaining syntax

Formatting and import ordering:

• Reformatted code for consistency and brevity, including single-line if/else blocks and multi-line assertions in src/graph.rs and src/ui.rs.
• Standardized import ordering in several files (src/graph.rs, src/main.rs, src/ui.rs) to group and alphabetize imports, improving clarity and maintainability.

[koharu-u]

Reviewed. migration from rust 2021 to 2024, Approved.