Add GUI scale sliders for Saturn's screens

The title screen, the menus and the HUD menus (emote wheel, shift menu)
each get a scale slider, relative to Minecraft's GUI scale. The HUD
editor stays in GUI pixels.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/main/java/org/saturnclient/ui/screens/ShiftMenu.java

@@ -3,6 +3,7 @@ package org.saturnclient.ui.screens;
 import org.saturnclient.common.provider.Providers;
 import org.saturnclient.config.AnimationConfig;
 import org.saturnclient.config.Config;
+import org.saturnclient.config.property.FloatProperty;
 import org.saturnclient.ui.SaturnScreen;
 import org.saturnclient.ui.anim.Fade;
 import org.saturnclient.ui.anim.SlideY;
@@ -24,6 +25,11 @@ public class ShiftMenu extends SaturnScreen {
         super("Shift Menu");
     }
 
+    @Override
+    protected FloatProperty getScaleSetting() {
+        return Config.hudMenuScale;
+    }
+
     @Override
     public void ui() {
         draw(new ImageTexture(Textures.LOGO_TEXT)