fix: move node-windows to optionalDependencies to fix Linux CI build

app-builder runs npm install --production inside the app dir during
packaging. node-windows has a Windows-only postinstall script that
fails on Linux with ENOENT. Moving it to optionalDependencies makes
npm treat install failures as non-fatal on non-Windows platforms.

Also simplify build-linux.yml — removes unnecessary app-builder binary
verification steps that were masking the actual root cause.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/desktop/package.json

@@ -18,13 +18,15 @@
   "dependencies": {
     "adm-zip": "^0.5.14",
     "axios": "^1.7.0",
-    "node-windows": "^1.0.0-beta.8",
     "sql.js": "^1.12.0",
     "qrcode": "^1.5.4",
     "ws": "^8.18.0",
     "xml2js": "^0.6.2",
     "xmlbuilder2": "^4.0.3"
   },
+  "optionalDependencies": {
+    "node-windows": "^1.0.0-beta.8"
+  },
   "devDependencies": {
     "@vitejs/plugin-react": "^4.3.0",
     "electron": "33.4.11",