🧹 Fix unsafe unwrap on file path conversion in CLI and GUI

Replaced `.to_str().unwrap()` with `.to_string_lossy()` when converting
`PathBuf` to `String` to prevent potential crashes if the path contains
invalid Unicode. This change improves the robustness of both the CLI
and GUI components when handling file paths.

- Modified `src/bin/cli.rs` to safely handle `file_path`.
- Modified `src/gui/mod.rs` to safely handle `path` in `play_file`.

Co-authored-by: arabianq <55220741+arabianq@users.noreply.github.com>

src/bin/cli.rs

@@ -144,7 +144,7 @@ async fn main() -> Result<(), Box<dyn Error>> {
             Actions::Play {
                 file_path,
                 concurrent,
-            } => Request::play(file_path.to_str().unwrap(), concurrent),
+            } => Request::play(&file_path.to_string_lossy(), concurrent),
             Actions::ToggleLoop { id } => Request::toggle_loop(id),
         },
         Commands::Get { parameter } => match parameter {