feat: add portable mode support and improve update handling

- Add portable.ini marker file creation in GitHub Actions for portable builds
- Implement is_portable_mode() command to detect portable execution
- Redirect portable users to GitHub releases page for manual updates
- Change update URL to point to latest releases page
- Integrate portable mode detection in Settings UI

src-tauri/src/lib.rs

@@ -377,6 +377,7 @@ pub fn run() {
             commands::get_settings,
             commands::save_settings,
             commands::check_for_updates,
+            commands::is_portable_mode,
             commands::get_vscode_settings_status,
             commands::read_vscode_settings,
             commands::write_vscode_settings,