test(desktop): add Vitest and testing dependencies

Install testing framework dependencies for unit testing:
- vitest@2.1.8 - Test runner
- @testing-library/react@16.1.0 - React component testing
- @testing-library/jest-dom@6.6.3 - Jest DOM matchers
- jsdom@25.0.1 - DOM simulation environment

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

desktop/package.json

@@ -47,16 +47,20 @@
     "@playwright/test": "^1.58.2",
     "@tailwindcss/vite": "^4.2.1",
     "@tauri-apps/cli": "^2",
+    "@testing-library/jest-dom": "6.6.3",
+    "@testing-library/react": "16.1.0",
     "@types/react": "^19.1.8",
     "@types/react-dom": "^19.1.6",
     "@types/react-window": "^2.0.0",
     "@types/uuid": "^10.0.0",
     "@vitejs/plugin-react": "^4.6.0",
     "autoprefixer": "^10.4.27",
+    "jsdom": "25.0.1",
     "playwright": "^1.58.2",
     "postcss": "^8.5.8",
     "tailwindcss": "^4.2.1",
     "typescript": "~5.8.3",
-    "vite": "^7.0.4"
+    "vite": "^7.0.4",
+    "vitest": "2.1.8"
   }
 }