Port UI icon textures from OpenGL to Vulkan, fix loading screen clear values

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)

include/rendering/vk_context.hpp

@@ -76,6 +76,12 @@ public:
     void setMsaaSamples(VkSampleCountFlagBits samples);
     VkSampleCountFlagBits getMaxUsableSampleCount() const;
 
+    // UI texture upload: creates a Vulkan texture from RGBA data and returns
+    // a VkDescriptorSet suitable for use as ImTextureID.
+    // The caller does NOT need to free the result — resources are tracked and
+    // cleaned up when the VkContext is destroyed.
+    VkDescriptorSet uploadImGuiTexture(const uint8_t* rgba, int width, int height);
+
 private:
     bool createInstance(SDL_Window* window);
     bool createSurface(SDL_Window* window);
@@ -144,6 +150,17 @@ private:
     VkRenderPass imguiRenderPass = VK_NULL_HANDLE;
     VkDescriptorPool imguiDescriptorPool = VK_NULL_HANDLE;
 
+    // Shared sampler for UI textures (created on first uploadImGuiTexture call)
+    VkSampler uiTextureSampler_ = VK_NULL_HANDLE;
+
+    // Tracked UI textures for cleanup
+    struct UiTexture {
+        VkImage image;
+        VkDeviceMemory memory;
+        VkImageView view;
+    };
+    std::vector<UiTexture> uiTextures_;
+
 #ifndef NDEBUG
     bool enableValidation = true;
 #else

include/ui/game_screen.hpp

@@ -8,7 +8,7 @@
 #include "ui/quest_log_screen.hpp"
 #include "ui/spellbook_screen.hpp"
 #include "ui/talent_screen.hpp"
-#include <GL/glew.h>
+#include <vulkan/vulkan.h>
 #include <imgui.h>
 #include <string>
 #include <unordered_map>
@@ -217,21 +217,21 @@ private:
     // WorldMap is now owned by Renderer (accessed via renderer->getWorldMap())
 
     // Spell icon cache: spellId -> GL texture ID
-    std::unordered_map<uint32_t, GLuint> spellIconCache_;
+    std::unordered_map<uint32_t, VkDescriptorSet> spellIconCache_;
     // SpellIconID -> icon path (from SpellIcon.dbc)
     std::unordered_map<uint32_t, std::string> spellIconPaths_;
     // SpellID -> SpellIconID (from Spell.dbc field 133)
     std::unordered_map<uint32_t, uint32_t> spellIconIds_;
     bool spellIconDbLoaded_ = false;
-    GLuint getSpellIcon(uint32_t spellId, pipeline::AssetManager* am);
+    VkDescriptorSet getSpellIcon(uint32_t spellId, pipeline::AssetManager* am);
 
     // Action bar drag state (-1 = not dragging)
     int actionBarDragSlot_ = -1;
-    GLuint actionBarDragIcon_ = 0;
+    VkDescriptorSet actionBarDragIcon_ = VK_NULL_HANDLE;
 
     // Bag bar state
-    GLuint backpackIconTexture_ = 0;
-    GLuint emptyBagSlotTexture_ = 0;
+    VkDescriptorSet backpackIconTexture_ = VK_NULL_HANDLE;
+    VkDescriptorSet emptyBagSlotTexture_ = VK_NULL_HANDLE;
     int bagBarPickedSlot_ = -1;   // Visual drag in progress (-1 = none)
     int bagBarDragSource_ = -1;   // Mouse pressed on this slot, waiting for drag or click (-1 = none)
 

include/ui/inventory_screen.hpp

@@ -3,7 +3,7 @@
 #include "game/inventory.hpp"
 #include "game/character.hpp"
 #include "game/world_packets.hpp"
-#include <GL/glew.h>
+#include <vulkan/vulkan.h>
 #include <imgui.h>
 #include <array>
 #include <functional>
@@ -93,9 +93,9 @@ private:
     pipeline::AssetManager* assetManager_ = nullptr;
 
     // Item icon cache: displayInfoId -> GL texture
-    std::unordered_map<uint32_t, GLuint> iconCache_;
+    std::unordered_map<uint32_t, VkDescriptorSet> iconCache_;
 public:
-    GLuint getItemIcon(uint32_t displayInfoId);
+    VkDescriptorSet getItemIcon(uint32_t displayInfoId);
 private:
 
     // Character model preview

include/ui/spellbook_screen.hpp

@@ -1,7 +1,7 @@
 #pragma once
 
 #include "game/game_handler.hpp"
-#include <GL/glew.h>
+#include <vulkan/vulkan.h>
 #include <imgui.h>
 #include <string>
 #include <vector>
@@ -41,7 +41,7 @@ public:
     // Drag-and-drop state for action bar assignment
     bool isDraggingSpell() const { return draggingSpell_; }
     uint32_t getDragSpellId() const { return dragSpellId_; }
-    void consumeDragSpell() { draggingSpell_ = false; dragSpellId_ = 0; dragSpellIconTex_ = 0; }
+    void consumeDragSpell() { draggingSpell_ = false; dragSpellId_ = 0; dragSpellIconTex_ = VK_NULL_HANDLE; }
 
 private:
     bool open = false;
@@ -55,7 +55,7 @@ private:
     // Icon data (loaded from SpellIcon.dbc)
     bool iconDbLoaded = false;
     std::unordered_map<uint32_t, std::string> spellIconPaths; // SpellIconID -> path
-    std::unordered_map<uint32_t, GLuint> spellIconCache;      // SpellIconID -> GL texture
+    std::unordered_map<uint32_t, VkDescriptorSet> spellIconCache;      // SpellIconID -> GL texture
 
     // Skill line data (loaded from SkillLine.dbc + SkillLineAbility.dbc)
     bool skillLineDbLoaded = false;
@@ -71,13 +71,13 @@ private:
     // Drag-and-drop from spellbook to action bar
     bool draggingSpell_ = false;
     uint32_t dragSpellId_ = 0;
-    GLuint dragSpellIconTex_ = 0;
+    VkDescriptorSet dragSpellIconTex_ = VK_NULL_HANDLE;
 
     void loadSpellDBC(pipeline::AssetManager* assetManager);
     void loadSpellIconDBC(pipeline::AssetManager* assetManager);
     void loadSkillLineDBCs(pipeline::AssetManager* assetManager);
     void categorizeSpells(const std::unordered_set<uint32_t>& knownSpells);
-    GLuint getSpellIcon(uint32_t iconId, pipeline::AssetManager* assetManager);
+    VkDescriptorSet getSpellIcon(uint32_t iconId, pipeline::AssetManager* assetManager);
     const SpellInfo* getSpellInfo(uint32_t spellId) const;
 };
 

include/ui/talent_screen.hpp

@@ -2,7 +2,7 @@
 
 #include "game/game_handler.hpp"
 #include <imgui.h>
-#include <GL/glew.h>
+#include <vulkan/vulkan.h>
 #include <unordered_map>
 #include <string>
 
@@ -25,7 +25,7 @@ private:
 
     void loadSpellDBC(pipeline::AssetManager* assetManager);
     void loadSpellIconDBC(pipeline::AssetManager* assetManager);
-    GLuint getSpellIcon(uint32_t iconId, pipeline::AssetManager* assetManager);
+    VkDescriptorSet getSpellIcon(uint32_t iconId, pipeline::AssetManager* assetManager);
 
     bool open = false;
     bool nKeyWasDown = false;
@@ -35,7 +35,7 @@ private:
     bool iconDbcLoaded = false;
     std::unordered_map<uint32_t, uint32_t> spellIconIds;  // spellId -> iconId
     std::unordered_map<uint32_t, std::string> spellIconPaths;  // iconId -> path
-    std::unordered_map<uint32_t, GLuint> spellIconCache;  // iconId -> texture
+    std::unordered_map<uint32_t, VkDescriptorSet> spellIconCache;  // iconId -> texture
     std::unordered_map<uint32_t, std::string> spellTooltips;  // spellId -> description
 };