refactor: config (#30)

* refactor(config): replace singleton with dependency injection

* refactor(client_player): return ChunkPosSet by value in non-const getter

Copy the internal set under the mutex lock to avoid exposing a mutable reference that could be used unsafely after the lock is released. This fixes a potential data race when the caller holds the returned reference beyond the critical section. Also update the caller in `client_world` to remove the now-unnecessary `std::move`.

* fix(gameplay): prevent use-after-free in pending delete queues during destruction

* refactor(config): separate game and server configuration with explicit paths

include/Cubed/audio/audio_engine.hpp

@@ -4,6 +4,7 @@
 #include "Cubed/audio/audio_source.hpp"
 #include "Cubed/audio/sound_manager.hpp"
 #include "Cubed/audio/source_pool.hpp"
+#include "Cubed/config.hpp"
 
 #include <AL/al.h>
 #include <AL/alc.h>
@@ -17,7 +18,7 @@ class ClientWorld;
 
 class AudioEngine {
 public:
-    AudioEngine();
+    AudioEngine(Config& config);
     AudioEngine(const AudioEngine&) = delete;
     AudioEngine(AudioEngine&&) = delete;
     AudioEngine& operator=(const AudioEngine&) = delete;
@@ -48,6 +49,7 @@ private:
     std::unique_ptr<AudioSource> m_bgm;
     FadeMap m_fade_map;
     SoundManager m_sounds;
+    Config& m_config;
     std::shared_ptr<SourcePool> m_pool;
     bool m_efx_supported = false;
     bool m_underwater = false;