Add single instance, remove box thing & change some styles & other stuff

src-tauri/Cargo.toml

@@ -18,3 +18,13 @@ serde = { version = "1.0.228", features = ["derive"] }
 serde_json = "1.0.150"
 tauri-plugin-clipboard-manager = "2.3.2"
 tauri-plugin-os = "2.3.2"
+
+[target.'cfg(not(any(target_os = "android", target_os = "ios")))'.dependencies]
+tauri-plugin-single-instance = "2.4.2"
+
+[profile.release]
+opt-level = 3
+lto = "fat"
+codegen-units = 1
+strip = true
+panic = "abort"