Add PWA support and responsive layout improvements:

- Integrate `vite-plugin-pwa` with automatic updates and manifest configuration for PWA support.
- Create `PWADownload.vue` component to guide users on installing the app.
- Add `/download` route in `router.js` for accessing the PWA download page.
- Improve responsive layout handling in `DefaultPageWrapper.vue` for better mobile adaptation.
- Update dependencies in `package.json` and `package-lock.json` to reflect PWA integration.

package.json

@@ -57,6 +57,7 @@
     "@vitejs/plugin-vue-jsx": "^4.1.2",
     "sass-embedded": "^1.81.0",
     "vite": "^5.4.10",
+    "vite-plugin-pwa": "^1.0.2",
     "vite-plugin-vue-devtools": "^7.5.4"
   }
 }