feat(server): add tokio udp runtime

crates/irtt-server/Cargo.toml

@@ -15,3 +15,4 @@ categories = ["network-programming"]
 irtt-proto.workspace = true
 getrandom = "0.4.3"
 thiserror = "2.0.20"
+tokio = { version = "1.53.1", default-features = false, features = ["rt", "net", "time", "sync", "macros"] }