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

CMakeLists.txt

@@ -18,8 +18,8 @@ find_package(glad REQUIRED)
 find_package(asio REQUIRED)
 find_package(glm REQUIRED)
 
-# Target setup
-add_executable(cuber "cuber.cpp"
+# OpenGL abstraction library
+add_library(cbt_opengl STATIC
     "cbt/opengl/context.cpp"
     "cbt/opengl/buffer.cpp"
     "cbt/opengl/texture.cpp"
@@ -27,8 +27,36 @@ add_executable(cuber "cuber.cpp"
     "cbt/opengl/shader.cpp"
     "cbt/opengl/vao.cpp"
 )
+target_include_directories(cbt_opengl PRIVATE ".")
+target_compile_features(cbt_opengl PRIVATE cxx_std_23)
+target_compile_options(cbt_opengl PRIVATE ${BASE_OPTIONS})
+target_compile_definitions(cbt_opengl PRIVATE ${BASE_DEFINITIONS})
+target_link_libraries(cbt_opengl PUBLIC fmt::fmt glfw::glfw glad::glad)
+
+# Scene base library
+add_library(cbt_scene STATIC
+    "cbt/scene.cpp"
+)
+target_include_directories(cbt_scene PRIVATE ".")
+target_compile_features(cbt_scene PRIVATE cxx_std_23)
+target_compile_options(cbt_scene PRIVATE ${BASE_OPTIONS})
+target_compile_definitions(cbt_scene PRIVATE ${BASE_DEFINITIONS})
+target_link_libraries(cbt_scene PUBLIC cbt_opengl)
+
+# Application scenes
+add_library(scenes_cube STATIC
+    "scenes/cube.cpp"
+)
+target_include_directories(scenes_cube PRIVATE ".")
+target_compile_features(scenes_cube PRIVATE cxx_std_23)
+target_compile_options(scenes_cube PRIVATE ${BASE_OPTIONS})
+target_compile_definitions(scenes_cube PRIVATE ${BASE_DEFINITIONS})
+target_link_libraries(scenes_cube PUBLIC cbt_scene glm::glm)
+
+# Main executable
+add_executable(cuber "cuber.cpp")
 target_include_directories(cuber PRIVATE ".")
 target_compile_features(cuber PRIVATE cxx_std_23)
 target_compile_options(cuber PRIVATE ${BASE_OPTIONS})
 target_compile_definitions(cuber PRIVATE ${BASE_DEFINITIONS})
-target_link_libraries(cuber PRIVATE fmt::fmt glfw::glfw glad::glad asio::asio glm::glm ${BASE_LIBRARIES})
+target_link_libraries(cuber PRIVATE cbt_scene scenes_cube asio::asio ${BASE_LIBRARIES})