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/texture.hpp

@@ -0,0 +1,57 @@
+#pragma once
+
+#include <cstddef>
+#include <vector>
+
+#include "glad/glad.h"
+
+namespace cbt::opengl {
+
+enum class texture_target {
+    _1d = GL_TEXTURE_1D,
+    _2d = GL_TEXTURE_2D,
+    _3d = GL_TEXTURE_3D,
+    cube = GL_TEXTURE_CUBE_MAP,
+};
+
+enum class texture_format {
+    rgb = GL_RGB,
+    rgba = GL_RGBA,
+    rg = GL_RG,
+    red = GL_RED,
+    depth = GL_DEPTH_COMPONENT,
+};
+
+enum class texture_type {
+    ubyte = GL_UNSIGNED_BYTE,
+    ushort = GL_UNSIGNED_SHORT,
+    uint = GL_UNSIGNED_INT,
+    float_ = GL_FLOAT,
+};
+
+class texture {
+    GLuint m_id = 0;
+    texture_target m_target = texture_target::_2d;
+
+public:
+    texture();
+    explicit texture(texture_target target);
+    ~texture();
+
+    texture(const texture&) = delete;
+    texture& operator=(const texture&) = delete;
+
+    texture(texture&& other) noexcept;
+    texture& operator=(texture&& other) noexcept;
+
+    auto bind(GLuint unit = 0) -> void;
+    auto unbind() -> void;
+    auto upload(const void* data, int width, int height, texture_format format, texture_type type) -> void;
+    auto set_filter(GLenum min_filter, GLenum mag_filter) -> void;
+    auto set_wrap(GLenum wrap_s, GLenum wrap_t) -> void;
+    auto generate_mipmaps() -> void;
+    auto id() const -> GLuint;
+    auto valid() const -> bool;
+};
+
+}