Rust 1.85.0 + Rust 2024 Edition (#68)

- Add `rust-toolchain.toml`
- Refactor `flake` to consider `rust-toolchain.toml`, especially Rust version
- `just`: Add run-sound command
- Ignore sound files
- Format

src/widgets/edit_time.rs

@@ -9,7 +9,7 @@ use ratatui::{
 
 use crate::{
     common::Style,
-    widgets::clock_elements::{Colon, Digit, COLON_WIDTH, DIGIT_SPACE_WIDTH, DIGIT_WIDTH},
+    widgets::clock_elements::{COLON_WIDTH, Colon, DIGIT_SPACE_WIDTH, DIGIT_WIDTH, Digit},
 };
 
 use super::clock_elements::DIGIT_HEIGHT;