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/dbc_loader.cpp

@@ -137,26 +137,32 @@ float DBCFile::getFloat(uint32_t recordIndex, uint32_t fieldIndex) const {
 }
 
 std::string DBCFile::getString(uint32_t recordIndex, uint32_t fieldIndex) const {
+    return std::string(getStringView(recordIndex, fieldIndex));
+}
+
+std::string_view DBCFile::getStringView(uint32_t recordIndex, uint32_t fieldIndex) const {
     uint32_t offset = getUInt32(recordIndex, fieldIndex);
-    return getStringByOffset(offset);
+    return getStringViewByOffset(offset);
 }
 
 std::string DBCFile::getStringByOffset(uint32_t offset) const {
+    return std::string(getStringViewByOffset(offset));
+}
+
+std::string_view DBCFile::getStringViewByOffset(uint32_t offset) const {
     if (!loaded || offset >= stringBlockSize) {
-        return "";
+        return {};
     }
 
-    // Find null terminator
     const char* str = reinterpret_cast<const char*>(stringBlock.data() + offset);
     const char* end = reinterpret_cast<const char*>(stringBlock.data() + stringBlockSize);
 
-    // Find string length (up to null terminator or end of block)
     size_t length = 0;
     while (str + length < end && str[length] != '\0') {
         length++;
     }
 
-    return std::string(str, length);
+    return std::string_view(str, length);
 }
 
 int32_t DBCFile::findRecordById(uint32_t id) const {