feat: Add authorization handlers and improve message retrieval limits

- Introduced NewAuthHandler and integrated it into the server routes.
- Added limit query parameter with default value handling in GetLatestMessages.
- Improved error handling for invalid limit values.
- Refactored Config struct to remove unnecessary fields and clean up loading logic.
- Updated Telegram client connection handling to enhance stability.

cmd/server/main.go

@@ -18,6 +18,7 @@ func main() {
 			server.NewGin,
 
 			handlers.NewChannelHandler,
+			handlers.NewAuthHandler,
 		),
 		telegram.Module,
 		fx.Invoke(server.RegisterRoutes),