fix(logic): immigrates LangSelectMenu to own controller

fix(println): also disappears the debug println statement from prod code
TODO: in the distant future, consider using a nice logging framework
(log4j?? or whatever spring boot is using..)

client/src/main/resources/client/scenes/FoodpalApplication.fxml

@@ -38,8 +38,7 @@
             <padding>
                 <Insets bottom="10" left="10" right="10" top="10" />
             </padding>
-            <ComboBox fx:id="langSelectMenu" onAction="#switchLocale">
-            </ComboBox>
+            <fx:include source="LangSelect.fxml" />
             <Button fx:id="refreshButton" onAction="#refresh" prefHeight="25.0" prefWidth="34.0" text="⟳" GridPane.columnIndex="3" GridPane.rowIndex="2" />
             <Label fx:id="recipesLabel" text="Recipes">
                 <font>

client/src/main/resources/client/scenes/LangSelect.fxml

@@ -0,0 +1,16 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<?import java.lang.*?>
+<?import java.util.*?>
+<?import javafx.scene.*?>
+<?import javafx.scene.control.*?>
+<?import javafx.scene.layout.*?>
+
+<ComboBox
+        fx:id="langSelectMenu"
+        xmlns="http://javafx.com/javafx/25"
+        xmlns:fx="http://javafx.com/fxml/1"
+        onAction="#switchLocale"
+        fx:controller="client.scenes.LangSelectMenuCtrl"
+>
+</ComboBox>