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

src/pipeline/mpq_manager.cpp

@@ -169,7 +169,7 @@ void MPQManager::shutdown() {
     archives.clear();
     archiveNames.clear();
     {
-        std::lock_guard<std::mutex> lock(fileArchiveCacheMutex_);
+        std::lock_guard<std::shared_mutex> lock(fileArchiveCacheMutex_);
         fileArchiveCache_.clear();
     }
     {
@@ -214,7 +214,7 @@ bool MPQManager::loadArchive(const std::string& path, int priority) {
 
     // Archive set/priority changed, so cached filename -> archive mappings may be stale.
     {
-        std::lock_guard<std::mutex> lock(fileArchiveCacheMutex_);
+        std::lock_guard<std::shared_mutex> lock(fileArchiveCacheMutex_);
         fileArchiveCache_.clear();
     }
 
@@ -383,7 +383,7 @@ HANDLE MPQManager::findFileArchive(const std::string& filename) const {
 #ifdef HAVE_STORMLIB
     std::string cacheKey = normalizeVirtualFilenameForLookup(filename);
     {
-        std::lock_guard<std::mutex> lock(fileArchiveCacheMutex_);
+        std::shared_lock<std::shared_mutex> lock(fileArchiveCacheMutex_);
         auto it = fileArchiveCache_.find(cacheKey);
         if (it != fileArchiveCache_.end()) {
             return it->second;
@@ -416,7 +416,7 @@ HANDLE MPQManager::findFileArchive(const std::string& filename) const {
     }
 
     {
-        std::lock_guard<std::mutex> lock(fileArchiveCacheMutex_);
+        std::lock_guard<std::shared_mutex> lock(fileArchiveCacheMutex_);
         if (fileArchiveCache_.size() >= fileArchiveCacheMaxEntries_) {
             // Simple safety valve: clear the cache rather than allowing an unbounded growth.
             LOG_WARNING("MPQ archive lookup cache cleared (size=", fileArchiveCache_.size(),