feat: integrate Mock Service Worker (MSW) for API mocking and testing

Currently just used for demo page

- Added MSW as a dependency in package.json.
- Configured MSW in the demo HTML to start the worker and handle API requests.
- Created mockServiceWorker.js to manage service worker lifecycle and request handling.
- Implemented browser.ts to set up the MSW worker with defined request handlers.
- Developed handlers.ts to simulate API responses and manage application state for testing.
diff --git a/webui/package.json b/webui/package.json
index 262a4fc..e865167 100644
--- a/webui/package.json
+++ b/webui/package.json
@@ -39,10 +39,16 @@
     "@web/test-runner-puppeteer": "^0.18.0",
     "autoprefixer": "^10.4.21",
     "esbuild": "^0.25.1",
+    "msw": "^2.7.5",
     "prettier": "3.5.3",
     "typescript": "^5.8.2",
     "vite": "^6.3.2",
     "vite-plugin-web-components-hmr": "^0.1.3"
   },
-  "keywords": []
+  "keywords": [],
+  "msw": {
+    "workerDirectory": [
+      ""
+    ]
+  }
 }