Updated the `HealthCheckHtmlGenerator` class to change the HTML auto-refresh countdown display from 10 seconds to 3 seconds. Adjusted the `countdown` variable in `health-ui.js` to initialize with 3 seconds, ensuring consistency between the frontend logic and the displayed countdown timer.
- Added `app.UseStaticFiles()` to serve static files from `wwwroot`.
- Changed root path redirection to `/health-ui`.
- Moved inline CSS/JS from `Program.cs` to `health-ui.css` and `health-ui.js`.
- Updated navigation links in the health check HTML.
- Enhanced Health UI with improved styles and animations.
- Introduced countdown auto-refresh in `health-ui.js`.
- Updated `launchSettings.json` to start at the root URL.
