Feat: clean the codebase as much as possible

src/bin/desktop/main.rs

@@ -275,7 +275,7 @@ impl CagireDesktop {
                     std::thread::Builder::new()
                         .name("sample-preload".into())
                         .spawn(move || {
-                            cagire::init::preload_sample_heads(preload_entries, sr, &registry);
+                            cagire::engine::preload_sample_heads(preload_entries, sr, &registry);
                         })
                         .expect("failed to spawn preload thread");
                 }