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

cbt/opengl/buffer.hpp

@@ -0,0 +1,41 @@
+#pragma once
+
+#include <cstddef>
+#include <vector>
+
+#include "glad/glad.h"
+
+namespace cbt::opengl {
+
+enum class buffer_type {
+    vertex = GL_ARRAY_BUFFER,
+    index = GL_ELEMENT_ARRAY_BUFFER,
+    uniform = GL_UNIFORM_BUFFER,
+    storage = GL_SHADER_STORAGE_BUFFER,
+};
+
+class buffer {
+    GLuint m_id = 0;
+    buffer_type m_type = buffer_type::vertex;
+
+public:
+    buffer();
+    explicit buffer(buffer_type type);
+    ~buffer();
+
+    buffer(const buffer&) = delete;
+    buffer& operator=(const buffer&) = delete;
+
+    buffer(buffer&& other) noexcept;
+    buffer& operator=(buffer&& other) noexcept;
+
+    auto bind() const -> void;
+    auto unbind() const -> void;
+    auto upload(const void* data, size_t size) -> void;
+    auto upload(std::vector<uint8_t> data) -> void;
+    auto upload_dynamic(const void* data, size_t size) -> void;
+    auto id() const -> GLuint;
+    auto valid() const -> bool;
+};
+
+}