Bundle WebView2Loader.dll so GNU-built installers run on clean machines

The GNU toolchain does not static-link WebView2Loader (unlike MSVC), so
the app failed to launch with a missing-DLL error. Ship the x64 loader as
a bundle resource installed next to the exe.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src-tauri/tauri.conf.json

@@ -26,6 +26,7 @@
   "bundle": {
     "active": true,
     "targets": ["nsis", "msi"],
+    "resources": ["WebView2Loader.dll"],
     "icon": [
       "icons/32x32.png",
       "icons/128x128.png",