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.cpp

@@ -0,0 +1,72 @@
+#include "cbt/opengl/buffer.hpp"
+
+#include "glad/glad.h"
+
+namespace cbt::opengl {
+
+buffer::buffer() {
+    glGenBuffers(1, &m_id);
+}
+
+buffer::buffer(buffer_type type)
+    : m_type(type) {
+    glGenBuffers(1, &m_id);
+}
+
+buffer::~buffer() {
+    if (m_id) {
+        glDeleteBuffers(1, &m_id);
+    }
+}
+
+buffer::buffer(buffer&& other) noexcept
+    : m_id(other.m_id)
+    , m_type(other.m_type) {
+    other.m_id = 0;
+}
+
+buffer& buffer::operator=(buffer&& other) noexcept {
+    if (this != &other) {
+        if (m_id) {
+            glDeleteBuffers(1, &m_id);
+        }
+        m_id = other.m_id;
+        m_type = other.m_type;
+        other.m_id = 0;
+    }
+    return *this;
+}
+
+auto buffer::bind() const -> void {
+    glBindBuffer(static_cast<GLenum>(m_type), m_id);
+}
+
+auto buffer::unbind() const -> void {
+    glBindBuffer(static_cast<GLenum>(m_type), 0);
+}
+
+auto buffer::upload(const void* data, size_t size) -> void {
+    bind();
+    glBufferData(static_cast<GLenum>(m_type), size, data, GL_STATIC_DRAW);
+    unbind();
+}
+
+auto buffer::upload(std::vector<uint8_t> data) -> void {
+    upload(data.data(), data.size());
+}
+
+auto buffer::upload_dynamic(const void* data, size_t size) -> void {
+    bind();
+    glBufferData(static_cast<GLenum>(m_type), size, data, GL_DYNAMIC_DRAW);
+    unbind();
+}
+
+auto buffer::id() const -> GLuint {
+    return m_id;
+}
+
+auto buffer::valid() const -> bool {
+    return m_id != 0;
+}
+
+}