feat: add OpenGL abstraction layer with RAII resources

- Replace window class with cbt::opengl::context
- Add buffer resource (VBO, EBO, UBO, SSBO) with move semantics
- Add texture resource with format/type enums and filtering
- Add descriptor_set for Vulkan-style resource binding
- All resources use RAII with proper cleanup

CMakeLists.txt

@@ -14,7 +14,12 @@ find_package(glad REQUIRED)
 find_package(asio REQUIRED)
 
 # Target setup
-add_executable(cuber "cuber.cpp" "cbt/window.cpp")
+add_executable(cuber "cuber.cpp"
+    "cbt/opengl/context.cpp"
+    "cbt/opengl/buffer.cpp"
+    "cbt/opengl/texture.cpp"
+    "cbt/opengl/descriptor.cpp"
+)
 target_include_directories(cuber PRIVATE ".")
 target_compile_features(cuber PRIVATE cxx_std_23)
 target_link_libraries(cuber PRIVATE fmt::fmt glfw::glfw glad::glad asio::asio)