zero-native has no Windows target yet, so add a parallel Tauri shell
for Windows that reuses the same frontend:
- src-tauri/: Rust commands (yt_search, yt_streams, store_load,
store_save) mirroring the Zig bridge; spawns bundled yt-dlp.exe with
CREATE_NO_WINDOW; data stored in app_data_dir
- frontend bridge now auto-detects window.__TAURI__ vs window.zero and
routes accordingly; CSP updated for Tauri IPC
- tauri.conf.json bundles yt-dlp.exe as a resource and builds nsis/msi
- scripts/make-icon.js generates appicon.png for 'tauri icon'
- README: native Windows build steps + WSLg fallback note
