fix: navigate main window after bridge ready to prevent white screen (#398)

When setup window starts the bridge, the main window was already created
with URL http://127.0.0.1:14168/ but failed to load (bridge not running yet).
After bridge becomes ready, we now navigate the main window to reload the
bridge URL before showing it, preventing the white screen issue.

frontends/desktop/src-tauri/src/lib.rs

@@ -196,7 +196,7 @@ fn ensure_bridge_running() {
 }
 
 #[tauri::command]
-fn start_bridge_with_config(python_path: String, project_dir: String) -> Result<(), String> {
+fn start_bridge_with_config(app_handle: tauri::AppHandle, python_path: String, project_dir: String) -> Result<(), String> {
     // Save to settings
     let path = settings_path();
     let obj = serde_json::json!({"python_path": python_path, "project_dir": project_dir});
@@ -222,6 +222,20 @@ fn start_bridge_with_config(python_path: String, project_dir: String) -> Result<
     if !wait_for_port(14168, Duration::from_secs(15)) {
         return Err("Bridge did not become ready within 15s".into());
     }
+
+    // Navigate main window to bridge URL and show it, hide setup
+    if let Some(main_win) = app_handle.get_webview_window("main") {
+        let url = tauri::Url::parse("http://127.0.0.1:14168/").unwrap();
+        let _ = main_win.navigate(url);
+        // Small delay for page to start loading
+        thread::sleep(Duration::from_millis(300));
+        let _ = main_win.show();
+        let _ = main_win.set_focus();
+    }
+    if let Some(setup_win) = app_handle.get_webview_window("setup") {
+        let _ = setup_win.hide();
+    }
+
     Ok(())
 }