### Summary of Changes
- Introduced theme-aware CSS variables for consistent styling across light and dark modes.
- Updated `App.jsx` to manage theme settings and improve layout responsiveness.
- Refactored `OfflineMode` component to provide detailed connection status and quick actions for users.
- Enhanced `Dashboard`, `Settings`, and `SystemMetrics` components to utilize new theme variables and improve UI consistency.
- Updated service URLs in constants and API documentation to reflect new configurations.
### Expected Results
- Improved user experience with a cohesive design that adapts to user preferences.
- Enhanced offline functionality, providing users with better feedback and control during service outages.
- Streamlined codebase with consistent styling practices, making future updates easier.
### Summary of Changes
- Replaced `react-query` with `@tanstack/react-query` in `package.json` and updated related imports.
- Updated frontend CI workflow to use `vitest` for testing instead of Jest, modifying test commands accordingly.
- Removed the `App.js`, `Dashboard.js`, `Settings.js`, and other component files, transitioning to a new structure.
- Enhanced error handling in the `useServiceStatus` hook to provide more informative error messages.
### Expected Results
- Improved performance and modernized the frontend build process with Vite.
- Streamlined testing setup with `vitest`, enhancing test execution speed and reliability.
- Increased clarity and maintainability of the codebase by adhering to clean code principles and removing unused components.
