Fix Rust build errors: use setup hook for window icon, enable image-png feature

The previous approach used Builder::default_window_icon() which doesn't
exist in Tauri 2.10. Instead, set the icon via window.set_icon() in the
setup hook, and enable the "image-png" feature flag so Image::from_bytes
can decode the PNG icon at runtime.

Also change bundle identifier from "com.triple-c.app" to
"com.triple-c.desktop" to avoid conflicting with the .app bundle
extension on macOS.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/src-tauri/src/lib.rs

@@ -18,7 +18,6 @@ pub fn run() {
     env_logger::init();
 
     tauri::Builder::default()
-        .default_window_icon(tauri::image::Image::from_bytes(include_bytes!("../icons/icon.png")).expect("Failed to load window icon"))
         .plugin(tauri_plugin_store::Builder::default().build())
         .plugin(tauri_plugin_dialog::init())
         .plugin(tauri_plugin_opener::init())
@@ -27,6 +26,14 @@ pub fn run() {
             settings_store: SettingsStore::new().expect("Failed to initialize settings store"),
             exec_manager: ExecSessionManager::new(),
         })
+        .setup(|app| {
+            let icon = tauri::image::Image::from_bytes(include_bytes!("../icons/icon.png"))
+                .expect("Failed to load window icon");
+            if let Some(window) = app.get_webview_window("main") {
+                let _ = window.set_icon(icon);
+            }
+            Ok(())
+        })
         .on_window_event(|window, event| {
             if let tauri::WindowEvent::CloseRequested { .. } = event {
                 let state = window.state::<AppState>();