refactor: complete OpenGL→Vulkan migration (Phase 7)

Remove all OpenGL/GLEW code and dependencies. The Vulkan renderer has
been the sole active backend for months; these files were dead code.

Deleted (8 files, 641 lines):
- rendering/mesh.cpp+hpp: OpenGL VAO/VBO/EBO wrapper (never instantiated)
- rendering/shader.cpp+hpp: OpenGL GLSL compiler (replaced by VkShaderModule)
- rendering/scene.cpp+hpp: Scene graph holding Mesh objects (created but
  never populated — all rendering uses Vulkan sub-renderers directly)
- rendering/video_player.cpp+hpp: FFmpeg+GL texture uploader (never
  included by any other file — login video feature can be re-implemented
  with VkTexture when needed)

Cleaned up:
- renderer.hpp: remove Scene forward-decl, getScene() accessor, scene member
- renderer.cpp: remove scene.hpp/shader.hpp includes, Scene create/destroy
- application.cpp: remove stale "GL/glew.h removed" comment
- CMakeLists.txt: remove find_package(OpenGL/GLEW), source/header entries,
  and target_link_libraries for OpenGL::GL and GLEW::GLEW
- PKGBUILD: remove glew dependency
- BUILD_INSTRUCTIONS.md: remove glew from all platform install commands

include/rendering/mesh.hpp

@@ -1,33 +0,0 @@
-#pragma once
-
-#include <vector>
-#include <GL/glew.h>
-#include <glm/glm.hpp>
-
-namespace wowee {
-namespace rendering {
-
-struct Vertex {
-    glm::vec3 position;
-    glm::vec3 normal;
-    glm::vec2 texCoord;
-};
-
-class Mesh {
-public:
-    Mesh() = default;
-    ~Mesh();
-
-    void create(const std::vector<Vertex>& vertices, const std::vector<uint32_t>& indices);
-    void destroy();
-    void draw() const;
-
-private:
-    GLuint VAO = 0;
-    GLuint VBO = 0;
-    GLuint EBO = 0;
-    size_t indexCount = 0;
-};
-
-} // namespace rendering
-} // namespace wowee

include/rendering/renderer.hpp

@@ -30,7 +30,6 @@ namespace rendering {
 
 class Camera;
 class CameraController;
-class Scene;
 class TerrainRenderer;
 class TerrainManager;
 class PerformanceHUD;
@@ -54,7 +53,6 @@ class Minimap;
 class WorldMap;
 class QuestMarkerRenderer;
 class CharacterPreview;
-class Shader;
 class AmdFsr3Runtime;
 
 class Renderer {
@@ -119,7 +117,6 @@ public:
 
     Camera* getCamera() { return camera.get(); }
     CameraController* getCameraController() { return cameraController.get(); }
-    Scene* getScene() { return scene.get(); }
     TerrainRenderer* getTerrainRenderer() const { return terrainRenderer.get(); }
     TerrainManager* getTerrainManager() const { return terrainManager.get(); }
     PerformanceHUD* getPerformanceHUD() { return performanceHUD.get(); }
@@ -219,7 +216,6 @@ private:
     core::Window* window = nullptr;
     std::unique_ptr<Camera> camera;
     std::unique_ptr<CameraController> cameraController;
-    std::unique_ptr<Scene> scene;
     std::unique_ptr<TerrainRenderer> terrainRenderer;
     std::unique_ptr<TerrainManager> terrainManager;
     std::unique_ptr<PerformanceHUD> performanceHUD;

include/rendering/scene.hpp

@@ -1,27 +0,0 @@
-#pragma once
-
-#include <vector>
-#include <memory>
-
-namespace wowee {
-namespace rendering {
-
-class Mesh;
-
-class Scene {
-public:
-    Scene() = default;
-    ~Scene() = default;
-
-    void addMesh(std::shared_ptr<Mesh> mesh);
-    void removeMesh(const std::shared_ptr<Mesh>& mesh);
-    void clear();
-
-    const std::vector<std::shared_ptr<Mesh>>& getMeshes() const { return meshes; }
-
-private:
-    std::vector<std::shared_ptr<Mesh>> meshes;
-};
-
-} // namespace rendering
-} // namespace wowee

include/rendering/shader.hpp

@@ -1,51 +0,0 @@
-#pragma once
-
-#include <string>
-#include <unordered_map>
-#include <GL/glew.h>
-#include <glm/glm.hpp>
-
-namespace wowee {
-namespace rendering {
-
-class Shader {
-public:
-    Shader() = default;
-    ~Shader();
-
-    [[nodiscard]] bool loadFromFile(const std::string& vertexPath, const std::string& fragmentPath);
-    [[nodiscard]] bool loadFromSource(const std::string& vertexSource, const std::string& fragmentSource);
-
-    void use() const;
-    void unuse() const;
-
-    void setUniform(const std::string& name, int value);
-    void setUniform(const std::string& name, float value);
-    void setUniform(const std::string& name, const glm::vec2& value);
-    void setUniform(const std::string& name, const glm::vec3& value);
-    void setUniform(const std::string& name, const glm::vec4& value);
-    void setUniform(const std::string& name, const glm::mat3& value);
-    void setUniform(const std::string& name, const glm::mat4& value);
-    void setUniformMatrixArray(const std::string& name, const glm::mat4* matrices, int count);
-
-    GLuint getProgram() const { return program; }
-
-    // Adopt an externally-created program (no ownership of individual shaders)
-    void setProgram(GLuint prog) { program = prog; }
-    // Release ownership without deleting (caller retains the GL program)
-    void releaseProgram() { program = 0; vertexShader = 0; fragmentShader = 0; }
-
-private:
-    bool compile(const std::string& vertexSource, const std::string& fragmentSource);
-    GLint getUniformLocation(const std::string& name) const;
-
-    GLuint program = 0;
-    GLuint vertexShader = 0;
-    GLuint fragmentShader = 0;
-
-    // Cache uniform locations to avoid expensive glGetUniformLocation calls
-    mutable std::unordered_map<std::string, GLint> uniformLocationCache;
-};
-
-} // namespace rendering
-} // namespace wowee

include/rendering/video_player.hpp

@@ -1,51 +0,0 @@
-#pragma once
-
-#include <string>
-#include <cstdint>
-#include <vector>
-
-typedef unsigned int GLuint;
-
-namespace wowee {
-namespace rendering {
-
-class VideoPlayer {
-public:
-    VideoPlayer();
-    ~VideoPlayer();
-
-    bool open(const std::string& path);
-    void update(float deltaTime);
-    void close();
-
-    bool isReady() const { return textureReady; }
-    GLuint getTextureId() const { return textureId; }
-    int getWidth() const { return width; }
-    int getHeight() const { return height; }
-
-private:
-    bool decodeNextFrame();
-    void uploadFrame();
-
-    void* formatCtx = nullptr;
-    void* codecCtx = nullptr;
-    void* frame = nullptr;
-    void* rgbFrame = nullptr;
-    void* packet = nullptr;
-    void* swsCtx = nullptr;
-
-    int videoStreamIndex = -1;
-    int width = 0;
-    int height = 0;
-    double frameTime = 1.0 / 30.0;
-    double accumulator = 0.0;
-    bool eof = false;
-
-    GLuint textureId = 0;
-    bool textureReady = false;
-    std::string sourcePath;
-    std::vector<uint8_t> rgbBuffer;
-};
-
-} // namespace rendering
-} // namespace wowee