Use unique_ptr to manage SDL pointers

src/core/engine.cppm

@@ -31,13 +31,11 @@ export namespace core
                 instantiated_ = true;
             }
 
-            // No copy operations
+            // No copy or move operations
             Engine(const Engine&) = delete;
             Engine& operator=(const Engine&) = delete;
-
-            // Default move operations
-            Engine(Engine&&) = default;
-            Engine& operator=(Engine&&) = default;
+            Engine(Engine&&) = delete;
+            Engine& operator=(Engine&&) = delete;
 
             ~Engine()
             {