Add loading screen with random WOWEE splash images

- Add loading screen system with stb_image for JPEG loading
- Two loading screen images (orc and dwarf) randomly selected
- Display loading screen while terrain data loads
- Cache WMO inverse matrices to reduce per-frame computation
- Stub WMO liquid rendering (needs coordinate system fix)
- Update spawn point to Stormwind Trade District

include/rendering/loading_screen.hpp

@@ -0,0 +1,50 @@
+#pragma once
+
+#include <GL/glew.h>
+#include <string>
+#include <vector>
+
+namespace wowee {
+namespace rendering {
+
+class LoadingScreen {
+public:
+    LoadingScreen();
+    ~LoadingScreen();
+
+    bool initialize();
+    void shutdown();
+
+    // Select a random loading screen image
+    void selectRandomImage();
+
+    // Render the loading screen (call in a loop while loading)
+    void render();
+
+    // Update loading progress (0.0 to 1.0)
+    void setProgress(float progress) { loadProgress = progress; }
+
+    // Set loading status text
+    void setStatus(const std::string& status) { statusText = status; }
+
+private:
+    bool loadImage(const std::string& path);
+    void createQuad();
+
+    GLuint textureId = 0;
+    GLuint vao = 0;
+    GLuint vbo = 0;
+    GLuint shaderId = 0;
+
+    std::vector<std::string> imagePaths;
+    int currentImageIndex = 0;
+
+    float loadProgress = 0.0f;
+    std::string statusText = "Loading...";
+
+    int imageWidth = 0;
+    int imageHeight = 0;
+};
+
+} // namespace rendering
+} // namespace wowee