Replace all glGenTextures/glTexImage2D calls in UI code with Vulkan texture
uploads via new VkContext::uploadImGuiTexture() helper. This fixes segfaults
from calling OpenGL functions without a GL context (null GLEW function pointers).
- Add uploadImGuiTexture() to VkContext with staging buffer upload pattern
- Convert game_screen, inventory_screen, spellbook_screen, talent_screen
from GLuint/GL calls to VkDescriptorSet/Vulkan uploads
- Fix loading_screen clearValueCount (was 1, needs 2 or 3 for MSAA)
Online world entry now shows a progress bar during character model,
terrain, and tile streaming. Fixed loading screen crash from calling
ImGui::NewFrame while a frame was already in progress. Log file is
now truncated on each launch instead of appending.
- 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
