perf: constexpr reciprocals, cache redundant lookups, consolidate texture maps

- Hoist DBC field index lookups before loops in game_handler (7 DBC iteration loops)
- Cache getSkybox()/getPosition() calls instead of redundant per-frame queries
- Merge textureHasAlphaByPtr_ + textureColorKeyBlackByPtr_ into single map
- Add constexpr for DEG_TO_RAD, reciprocal constants, physics delta
- Add reserve() for WMO/M2 collision grid queries and portal BFS
- Frustum plane normalize: inversesqrt instead of length+divide
- M2 particle emission: inversesqrt for direction normalization
- Parse creature display IDs from query response
- UI: show spell names/IDs as fallback instead of "Unknown"

include/rendering/character_renderer.hpp

@@ -293,8 +293,11 @@ private:
         bool normalMapPending = false;  // deferred normal map generation
     };
     std::unordered_map<std::string, TextureCacheEntry> textureCache;
-    std::unordered_map<VkTexture*, bool> textureHasAlphaByPtr_;
-    std::unordered_map<VkTexture*, bool> textureColorKeyBlackByPtr_;
+    struct TextureProperties {
+        bool hasAlpha = false;
+        bool colorKeyBlack = false;
+    };
+    std::unordered_map<VkTexture*, TextureProperties> texturePropsByPtr_;
     std::unordered_map<std::string, VkTexture*> compositeCache_;  // key → texture for reuse
     std::unordered_set<std::string> failedTextureCache_;  // negative cache for budget exhaustion
     std::unordered_map<std::string, uint64_t> failedTextureRetryAt_;

include/rendering/m2_renderer.hpp

@@ -483,8 +483,11 @@ private:
         bool colorKeyBlack = false;
     };
     std::unordered_map<std::string, TextureCacheEntry> textureCache;
-    std::unordered_map<VkTexture*, bool> textureHasAlphaByPtr_;
-    std::unordered_map<VkTexture*, bool> textureColorKeyBlackByPtr_;
+    struct TextureProperties {
+        bool hasAlpha = false;
+        bool colorKeyBlack = false;
+    };
+    std::unordered_map<VkTexture*, TextureProperties> texturePropsByPtr_;
     size_t textureCacheBytes_ = 0;
     uint64_t textureCacheCounter_ = 0;
     size_t textureCacheBudgetBytes_ = 2048ull * 1024 * 1024;