feat: async mDNS discovery; emit device events; auto-build sidecar in npm dev

src-tauri/Cargo.toml

@@ -25,6 +25,8 @@ serde = { version = "1", features = ["derive"] }
 serde_json = "1"
 rust_cast = "0.19.0"
 mdns-sd = "0.17.1"
+agnostic-mdns = { version = "0.4", features = ["tokio"] }
+async-channel = "2.5.0"
 tokio = { version = "1.48.0", features = ["full"] }
 tauri-plugin-shell = "2.3.3"
 reqwest = { version = "0.11", features = ["json", "rustls-tls"] }