refactor(gameplay): split world into client and server

Remove monolithic World, Player, Chunk classes. Introduce ClientWorld, ServerWorld, ClientPlayer, and related networked components. Add Abseil dependency for logging and checks. Rename old files to pre_remove_* and update all includes and references accordingly.

src/gameplay/network_client.cpp

@@ -4,7 +4,7 @@
 #include "Cubed/tools/log.hpp"
 namespace Cubed {
 NetworkClient::NetworkClient(ClientWorld& world)
-    : m_socket(m_io), m_world(world) {}
+    : m_socket(m_io), m_strand(asio::make_strand(m_io)), m_world(world) {}
 
 NetworkClient::~NetworkClient() { close(); }