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

src/rendering/water_renderer.cpp

@@ -2,6 +2,7 @@
 #include "rendering/shader.hpp"
 #include "rendering/camera.hpp"
 #include "pipeline/adt_loader.hpp"
+#include "pipeline/wmo_loader.hpp"
 #include "core/logger.hpp"
 #include <GL/glew.h>
 #include <glm/gtc/matrix_transform.hpp>
@@ -209,6 +210,16 @@ void WaterRenderer::removeTile(int tileX, int tileY) {
     }
 }
 
+void WaterRenderer::loadFromWMO([[maybe_unused]] const pipeline::WMOLiquid& liquid,
+                                 [[maybe_unused]] const glm::mat4& modelMatrix,
+                                 [[maybe_unused]] uint32_t wmoId) {
+    // WMO liquid rendering not yet implemented
+}
+
+void WaterRenderer::removeWMO([[maybe_unused]] uint32_t wmoId) {
+    // WMO liquid rendering not yet implemented
+}
+
 void WaterRenderer::clear() {
     for (auto& surface : surfaces) {
         destroyWaterMesh(surface);