fix(desktop): remove instalacao WebView2 para evitar UAC duplo

Windows 10/11 ja possuem WebView2 pre-instalado. Usar "skip" elimina
o segundo prompt de UAC durante a instalacao.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/desktop/src-tauri/tauri.conf.json

@@ -52,8 +52,7 @@
     ],
     "windows": {
       "webviewInstallMode": {
-        "type": "downloadBootstrapper",
-        "silent": true
+        "type": "skip"
       },
       "nsis": {
         "displayLanguageSelector": true,