Optimize release builds: LTO, -O3, visibility, micro-perf fixes

- CMakeLists.txt: enable LTO for Release, add -O3 and -fvisibility=hidden
- scene: addMesh uses std::move, removeMesh takes const shared_ptr&
- entity: std::move entity into map instead of copy
- clouds: cosf/sinf instead of cos/sin (float math, avoids double promotion)
- game_screen: reserve trainer spell vector before push_back loop
- warden_module/emulator: replace std::endl (121 stream flushes) with '\n'

src/game/entity.cpp

@@ -10,7 +10,7 @@ void EntityManager::addEntity(uint64_t guid, std::shared_ptr<Entity> entity) {
         return;
     }
 
-    entities[guid] = entity;
+    entities[guid] = std::move(entity);
 
     LOG_DEBUG("Added entity: GUID=0x", std::hex, guid, std::dec,
               ", Type=", static_cast<int>(entity->getType()));