refactor: split network config into game_host and listen_addr

Replace RUSTY_TELEMETRY_BIND with two env vars:
- RUSTY_TELEMETRY_GAME_HOST: IP of the machine running the sim (for
  KSUDP handshake target). Default: 127.0.0.1
- RUSTY_TELEMETRY_LISTEN: local address to bind for incoming feeds
  (Telemetry Tool, PCARS). Default: 0.0.0.0 (accept from any interface)

Both fall back to RUSTY_TELEMETRY_BIND for backward compatibility.
This enables running rusty-telemetry on a separate machine from the game.

src/main.rs

@@ -45,8 +45,23 @@ fn decode_utf16le(bytes: &[u8]) -> String {
     String::from_utf16_lossy(&chars)
 }
 
-fn bind_addr() -> String {
-    std::env::var("RUSTY_TELEMETRY_BIND").unwrap_or_else(|_| "127.0.0.1".to_string())
+/// IP address of the machine running the sim game.
+/// Used as the KSUDP handshake target (AC binds :9996 on this host).
+/// Default: 127.0.0.1 (local — game and listener on same machine).
+/// Set to e.g. 192.168.1.2 when the game runs on a different machine.
+fn game_host() -> String {
+    std::env::var("RUSTY_TELEMETRY_GAME_HOST")
+        .or_else(|_| std::env::var("RUSTY_TELEMETRY_BIND"))
+        .unwrap_or_else(|_| "127.0.0.1".to_string())
+}
+
+/// Local address to bind for incoming UDP feeds (Telemetry Tool, PCARS).
+/// Default: 0.0.0.0 (accept from any interface — works for both local and remote).
+/// Set to 127.0.0.1 to only accept local packets.
+fn listen_addr() -> String {
+    std::env::var("RUSTY_TELEMETRY_LISTEN")
+        .or_else(|_| std::env::var("RUSTY_TELEMETRY_BIND"))
+        .unwrap_or_else(|_| "0.0.0.0".to_string())
 }
 
 #[derive(Clone)]
@@ -113,15 +128,15 @@ async fn run_feed(
     shutdown: Arc<tokio::sync::Notify>,
 ) {
     let handshake_target: Option<std::net::SocketAddr> = if feed.needs_handshake {
-        let target: std::net::SocketAddr = match format!("{}:{}", bind_addr(), feed.port).parse() {
+        let target: std::net::SocketAddr = match format!("{}:{}", game_host(), feed.port).parse() {
             Ok(addr) => addr,
             Err(e) => {
                 eprintln!(
-                    "[ERROR] {} :{} Invalid target address '{}': {}",
-                    feed.label, feed.port, bind_addr(), e
+                    "[ERROR] {} :{} Invalid game host address '{}': {}",
+                    feed.label, feed.port, game_host(), e
                 );
                 if let Ok(mut s) = state.lock() {
-                    s.set_error(&format!("Invalid target address: {}", e));
+                    s.set_error(&format!("Invalid game host address: {}", e));
                 }
                 return;
             }
@@ -357,7 +372,7 @@ async fn run_feed(
 async fn main() {
     install_panic_hook();
 
-    let bind = bind_addr();
+    let listen = listen_addr();
     let session_id = chrono::Local::now().format("%Y%m%d_%H%M%S").to_string();
     let session_dir = format!("./data/{}", session_id);
 
@@ -382,7 +397,7 @@ async fn main() {
         let state = Arc::new(std::sync::Mutex::new(FeedState::new()));
 
         let (socket_opt, mode) = if feed.needs_handshake {
-            let recv_addr = format!("{}:0", bind);
+            let recv_addr = format!("{}:0", listen);
             match tokio::net::UdpSocket::bind(&recv_addr).await {
                 Ok(s) => {
                     let local_port = s.local_addr().map(|a| a.port()).unwrap_or(0);
@@ -406,7 +421,7 @@ async fn main() {
                 }
             }
         } else {
-            let addr = format!("{}:{}", bind, feed.port);
+            let addr = format!("{}:{}", listen, feed.port);
             match tokio::net::UdpSocket::bind(&addr).await {
                 Ok(s) => (Some(s), FeedMode::BindListen),
                 Err(e) => {