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/vite-env.d.ts

@@ -39,6 +39,7 @@ declare global {
       getSettings: () => Promise<Settings>;
       saveSettings: (settings: Settings) => Promise<boolean>;
       checkForUpdates: () => Promise<void>;
+      isPortable: () => Promise<boolean>;
       getAppConfigPath: () => Promise<string>;
       openAppConfigFolder: () => Promise<void>;
       // VS Code settings.json 能力