feat(tauri): add single instance plugin and improve code formatting

This update introduces the tauri-plugin-single-instance to ensure that
only one instance of the application can run at a time. Additionally,
the code has been reformatted for better readability, with consistent
line breaks and spacing.

- Added single instance plugin to prevent multiple app instances
- Improved code formatting for better readability and maintenance
- Updated dependencies in Cargo.toml for new plugin integration

src-tauri/Cargo.toml

@@ -26,6 +26,7 @@ tokio = "1.52.3"
 tauri-build = { version = "2", features = [] }
 
 [target.'cfg(not(any(target_os = "android", target_os = "ios")))'.dependencies]
+tauri-plugin-single-instance = "2"
 tauri-plugin-updater = "2"
 
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