Add Windows support via a Tauri (WebView2) shell

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

package.json

@@ -1,11 +1,18 @@
 {
   "name": "ytplayer",
   "version": "1.0.0",
-  "description": "Ad-free YouTube player with local playlists. No login, no ads, direct streams via yt-dlp. Built on zero-native (Zig + system WebView).",
+  "description": "Ad-free YouTube player with local playlists. No login, no ads, direct streams via yt-dlp. zero-native (Linux/macOS) and Tauri (Windows) shells.",
   "scripts": {
     "setup": "node scripts/setup-ytdlp.js",
-    "update-ytdlp": "node scripts/setup-ytdlp.js --force"
+    "update-ytdlp": "node scripts/setup-ytdlp.js --force",
+    "make-icon": "node scripts/make-icon.js",
+    "tauri": "tauri",
+    "tauri:dev": "tauri dev",
+    "tauri:build": "tauri build"
   },
   "author": "",
-  "license": "MIT"
+  "license": "MIT",
+  "devDependencies": {
+    "@tauri-apps/cli": "^2"
+  }
 }