Introduced LoggerMiddleware for HTTP request logging. Refactored handler
methods to return http.HandlerFunc for improved composability. Updated
route registration and tests to use new handler signatures.
Refactored web server to move route registration into a dedicated method
and extracted static CSS into its own file for better maintainability.
Updated HTML template to use external stylesheet and improved JS code
style consistency. This enhances separation of concerns and prepares
for easier future asset management.
