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/core/logger.cpp

@@ -124,10 +124,11 @@ void Logger::log(LogLevel level, const std::string& message) {
         return;
     }
 
+    // Capture timestamp before acquiring lock to minimize critical section
+    auto nowSteady = std::chrono::steady_clock::now();
+
     std::lock_guard<std::mutex> lock(mutex);
     ensureFile();
-
-    auto nowSteady = std::chrono::steady_clock::now();
     if (dedupeEnabled_ && !lastMessage_.empty() &&
         level == lastLevel_ && message == lastMessage_) {
         auto elapsedMs = std::chrono::duration_cast<std::chrono::milliseconds>(nowSteady - lastMessageTime_).count();