Fix and complete JavaDoc comments

src/main/java/it/polimi/ingsw/gc14/HelloApplication.java

@@ -7,7 +7,17 @@ import javafx.stage.Stage;
 
 import java.io.IOException;
 
+/**
+ * JavaFX application entry point used to start the graphical interface.
+ */
 public class HelloApplication extends Application {
+
+    /**
+     * Starts the JavaFX application and loads the initial FXML view.
+     *
+     * @param stage the primary stage of the application.
+     * @throws IOException if the FXML file cannot be loaded.
+     */
     @Override
     public void start(Stage stage) throws IOException {
         FXMLLoader fxmlLoader = new FXMLLoader(HelloApplication.class.getResource("hello-view.fxml"));