feat: 초기 커밋

- Progress Quest 6.4 Flutter 포팅 프로젝트
- 게임 루프, 상태 관리, UI 구현
- 캐릭터 생성, 인벤토리, 장비, 주문 시스템
- 시장/판매/구매 메커니즘

linux/runner/my_application.h

@@ -0,0 +1,18 @@
+#ifndef FLUTTER_MY_APPLICATION_H_
+#define FLUTTER_MY_APPLICATION_H_
+
+#include <gtk/gtk.h>
+
+G_DECLARE_FINAL_TYPE(MyApplication, my_application, MY, APPLICATION,
+                     GtkApplication)
+
+/**
+ * my_application_new:
+ *
+ * Creates a new Flutter-based application.
+ *
+ * Returns: a new #MyApplication.
+ */
+MyApplication* my_application_new();
+
+#endif  // FLUTTER_MY_APPLICATION_H_