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/pipeline/asset_manager.hpp

@@ -8,7 +8,9 @@
 #include <string>
 #include <vector>
 #include <map>
+#include <unordered_map>
 #include <mutex>
+#include <shared_mutex>
 
 namespace wowee {
 namespace pipeline {
@@ -164,15 +166,15 @@ private:
      */
     std::string resolveFile(const std::string& normalizedPath) const;
 
-    mutable std::mutex cacheMutex;
-    std::map<std::string, std::shared_ptr<DBCFile>> dbcCache;
+    mutable std::shared_mutex cacheMutex;
+    std::unordered_map<std::string, std::shared_ptr<DBCFile>> dbcCache;
 
     // File cache (LRU, dynamic budget based on system RAM)
     struct CachedFile {
         std::vector<uint8_t> data;
         uint64_t lastAccessTime;
     };
-    mutable std::map<std::string, CachedFile> fileCache;
+    mutable std::unordered_map<std::string, CachedFile> fileCache;
     mutable size_t fileCacheTotalBytes = 0;
     mutable uint64_t fileCacheAccessCounter = 0;
     mutable size_t fileCacheHits = 0;