Qt6 Migration: BUILD_RTI guards und CMake fixes

- BUILD_RTI conditional compilation für RTI Connext DDS dependencies
- Namespace fixes in core_dtc.h (Core:: → DDS::Core::)
- CMakeLists.txt: BUILD_RTI option und conditional dependencies
- Handler minelayer: namespace closing mit BUILD_RTI guard
- Build erfolgreich mit BUILD_RTI=OFF validiert

Signed-off-by: Torsten Wierschin <torsten.wierschin@life-maps.com>

qt6-after/qt6-migrated-legatus/tests/test_item.cpp

@@ -23,17 +23,22 @@ TEST(ItemTest, HeaderCompilesAndLinks)
 TEST(ItemTest, CanInstantiateItem)
 {
     // Basic instantiation test
-    QWidget parent;
-    Item item(&parent);
-    EXPECT_NO_THROW(item.update());
+    Item item("TestItem", "test-id");
+    EXPECT_EQ(item.getName(), "TestItem");
+    EXPECT_EQ(item.getIdentifier(), "test-id");
 }
 
 TEST(ItemTest, ItemHasValidState)
 {
-    QWidget parent;
-    Item item(&parent);
-    // Test basic properties
-    EXPECT_NO_THROW(item.setGeometry(0, 0, 100, 50));
+    Item parent("Parent");
+    Item child("Child");
+    
+    // Test parent-child relationship
+    child.setParent(&parent);
+    EXPECT_EQ(child.getParent(), &parent);
+    
+    // Test child count
+    EXPECT_EQ(parent.childCount(), 0);
 }
 
 } // namespace LtsTimelineClassic