Add 3D character model preview to character creation screen

Render an animated M2 character model in the creation screen using a
dedicated CharacterRenderer with an offscreen FBO. Preview updates on
race/gender/appearance changes, supports mouse-drag rotation, and
composites skin, face, hair scalp, and underwear textures from
CharSections.dbc. Extracts getPlayerModelPath() to a shared free
function in game/character.

include/rendering/character_preview.hpp

@@ -0,0 +1,57 @@
+#pragma once
+
+#include "game/character.hpp"
+#include <GL/glew.h>
+#include <memory>
+#include <cstdint>
+
+namespace wowee {
+namespace pipeline { class AssetManager; }
+namespace rendering {
+
+class CharacterRenderer;
+class Camera;
+
+class CharacterPreview {
+public:
+    CharacterPreview();
+    ~CharacterPreview();
+
+    bool initialize(pipeline::AssetManager* am);
+    void shutdown();
+
+    bool loadCharacter(game::Race race, game::Gender gender,
+                       uint8_t skin, uint8_t face,
+                       uint8_t hairStyle, uint8_t hairColor,
+                       uint8_t facialHair);
+
+    void update(float deltaTime);
+    void render();
+    void rotate(float yawDelta);
+
+    GLuint getTextureId() const { return colorTexture_; }
+    int getWidth() const { return fboWidth_; }
+    int getHeight() const { return fboHeight_; }
+
+private:
+    void createFBO();
+    void destroyFBO();
+
+    pipeline::AssetManager* assetManager_ = nullptr;
+    std::unique_ptr<CharacterRenderer> charRenderer_;
+    std::unique_ptr<Camera> camera_;
+
+    GLuint fbo_ = 0;
+    GLuint colorTexture_ = 0;
+    GLuint depthRenderbuffer_ = 0;
+    static constexpr int fboWidth_ = 400;
+    static constexpr int fboHeight_ = 500;
+
+    static constexpr uint32_t PREVIEW_MODEL_ID = 9999;
+    uint32_t instanceId_ = 0;
+    bool modelLoaded_ = false;
+    float modelYaw_ = 180.0f;
+};
+
+} // namespace rendering
+} // namespace wowee