feat: add macOS desktop client build workflow with ARM64 support and fix tunnel metrics task ownership

Add macos-desktop-client.yml workflow with manual dispatch trigger running on macos-arm64 runner. Install Node.js 22 and Rust toolchain with aarch64-apple-darwin target. Build bundled tunnel helper and Tauri application bundle, then upload .app, .dmg, and raw build artifacts.

Fix tunnel_metrics handler to clone app handle before spawn_blocking to prevent ownership issues when passing to tunnel

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

@@ -486,8 +486,9 @@ async fn tunnel_metrics(app: AppHandle, state: State<'_, AppState>) -> Result<Tu
         let session = session.as_ref().ok_or_else(|| "No active session is available".to_string())?;
         session.profile_path.clone()
     };
+    let metrics_app = app.clone();
     let metrics = tauri::async_runtime::spawn_blocking(move || {
-        tunnel_manager::metrics(&app, std::path::Path::new(&profile_path))
+        tunnel_manager::metrics(&metrics_app, std::path::Path::new(&profile_path))
     })
     .await
     .map_err(|err| format!("Unable to join tunnel metrics task: {err}"))??;