新增: df-relay binary 入口(main.rs axum WS Server :8080)

Phase3 联调链补 relay 启动入口:src/main.rs 调 DefaultRelayServer::start(listen 0.0.0.0:8080,DF_RELAY_ADDR env 覆盖)+ tracing-subscriber 日志。cargo run -p df-relay 启动,提供 /ws/device + /ws/miniapp 端点。cargo check EXIT=0。

crates/df-relay/Cargo.toml

@@ -12,6 +12,8 @@ async-trait = { workspace = true }
 thiserror = { workspace = true }
 anyhow = { workspace = true }
 tracing = { workspace = true }
+# binary 入口(main.rs)日志初始化
+tracing-subscriber = { version = "0.3", features = ["env-filter"] }
 
 # HTTP + WS 服务端
 axum = { version = "0.7", features = ["ws"] }