refactor: split into static libraries and restructure scenes

- Create cbt_opengl static library for OpenGL abstraction
- Create cbt_scene static library for base scene class
- Create scenes_cube static library for cube scene
- Move scene base to cbt/ (utility), scenes to root scenes/
- Link libraries in dependency chain: cuber -> scenes -> cbt_scene -> cbt_opengl

scenes/cube.hpp

@@ -0,0 +1,34 @@
+#pragma once
+
+#include "cbt/scene.hpp"
+
+#include "cbt/opengl/shader.hpp"
+#include "cbt/opengl/buffer.hpp"
+#include "cbt/opengl/vao.hpp"
+
+#include <glm/glm.hpp>
+
+namespace cbt::scenes {
+
+class cube final : public scene {
+    opengl::shader m_prog;
+    opengl::buffer m_vbo;
+    opengl::vao m_vao;
+
+    GLint m_loc_proj = -1;
+    GLint m_loc_view = -1;
+    GLint m_loc_model = -1;
+
+    std::chrono::steady_clock::time_point m_start;
+
+    auto build_mesh() -> void;
+    auto build_shader() -> bool;
+
+public:
+    cube();
+    auto init() -> bool override;
+    auto update(float delta_time) -> void override;
+    auto render() -> void override;
+};
+
+}