Implemented durationMode in TimeSpinner3D and added unit test.

- In `TimeSpinner3D.java`:
    - Implemented `setDurationMode(boolean)` to update state and rebuild UI.
    - Updated `addComponents` to add "hours" and "minutes" labels in duration mode.
    - Updated `rebuildHours` to set correct hour range (0-24) for duration mode.
- Added `TimeSpinner3DTest.java` in `maven/core-unittests` to verify duration mode behavior.

Author: google-labs-jules[bot]

maven/core-unittests/src/test/java/com/codename1/ui/spinner/TimeSpinner3DTest.java

@@ -0,0 +1,51 @@
+package com.codename1.ui.spinner;
+
+import com.codename1.ui.Component;
+import com.codename1.ui.Display;
+import com.codename1.ui.Form;
+import com.codename1.ui.Label;
+import com.codename1.ui.layouts.LayeredLayout;
+import com.codename1.junit.UITestBase;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class TimeSpinner3DTest extends UITestBase {
+
+    @Test
+    public void testDurationMode() {
+        TimeSpinner3D ts = new TimeSpinner3D();
+        ts.setDurationMode(true);
+
+        Assertions.assertTrue(ts.isDurationMode(), "durationMode should be true");
+        Assertions.assertFalse(ts.isShowMeridiem(), "showMeridiem should be false in duration mode");
+
+        // Check components
+        // In duration mode we expect: Hour spinner, Hour label, Minute spinner, Minute label
+        // That is 4 components.
+
+        Assertions.assertEquals(4, ts.getComponentCount(), "Should have 4 components in duration mode");
+
+        boolean foundHoursLabel = false;
+        boolean foundMinutesLabel = false;
+
+        for (int i = 0; i < ts.getComponentCount(); i++) {
+            Component c = ts.getComponentAt(i);
+            if (c instanceof Label) {
+                Label l = (Label) c;
+                if ("hours".equals(l.getText()) || "hours".equals(l.getUIID())) {
+                   if ("TimeSpinnerHoursLabel".equals(l.getUIID())) {
+                       foundHoursLabel = true;
+                   }
+                }
+                if ("minutes".equals(l.getText()) || "minutes".equals(l.getUIID())) {
+                   if ("TimeSpinnerMinutesLabel".equals(l.getUIID())) {
+                       foundMinutesLabel = true;
+                   }
+                }
+            }
+        }
+
+        Assertions.assertTrue(foundHoursLabel, "Should find hours label");
+        Assertions.assertTrue(foundMinutesLabel, "Should find minutes label");
+    }
+}