perf: eliminate ~70 unnecessary sqrt ops per frame, optimize caches and threading

Squared distance optimizations across 30 files:
- Convert glm::length() comparisons to glm::dot() (no sqrt)
- Use glm::inversesqrt() for check-then-normalize patterns (1 rsqrt vs 2 sqrt)
- Defer sqrt to after early-out checks in collision/movement code
- Hottest paths: camera_controller (21), weather particles, WMO collision,
  transport movement, creature interpolation, nameplate culling

Container and algorithm improvements:
- std::map<string> → std::unordered_map for asset/DBC/MPQ/warden caches
- std::mutex → std::shared_mutex for asset_manager and mpq_manager caches
- std::sort → std::partial_sort in lighting_manager (top-2 of N volumes)
- Double-lookup find()+operator[] → insert_or_assign in game_handler
- Add reserve() for per-frame vectors: weather, swim_effects, WMO/M2 collision

Threading and synchronization:
- Replace 1ms busy-wait polling with condition_variable in character_renderer
- Move timestamp capture before mutex in logger
- Use memory_order_acquire/release for normal map completion signaling

API additions:
- DBC getStringView()/getStringViewByOffset() for zero-copy string access
- Parse creature display IDs from SMSG_CREATURE_QUERY_SINGLE_RESPONSE

include/rendering/character_renderer.hpp

@@ -13,6 +13,7 @@
 #include <utility>
 #include <future>
 #include <deque>
+#include <condition_variable>
 #include <mutex>
 #include <atomic>
 
@@ -325,6 +326,7 @@ private:
     };
     // Completed results ready for GPU upload (populated by background threads)
     std::mutex normalMapResultsMutex_;
+    std::condition_variable normalMapDoneCV_;  // signaled when pendingNormalMapCount_ reaches 0
     std::deque<NormalMapResult> completedNormalMaps_;
     std::atomic<int> pendingNormalMapCount_{0};  // in-flight background tasks