refactor(upload): route upload commands to dedicated handler

src/upload.rs

@@ -0,0 +1,11 @@
+use tokio::{io, net::TcpStream, stream};
+
+use crate::protocol::Header;
+
+pub async fn handle(
+    stream: &mut TcpStream,
+    header: Header,
+) -> io::Result<()> {
+    println!("Обработчик UPLOAD получил заголовок: {header:?}");
+    Ok(())
+}