v0.5.0: Add syslog support, fix TCP send/both, EC-SRP5 server auth

New features:
- --syslog <address:port> sends structured events to remote syslog (RFC 5424 UDP)
  Events: AUTH_SUCCESS, AUTH_FAILURE, TEST_START, TEST_END, TEST_RESULT
- EC-SRP5 authentication for both client and server modes
- TCP multi-connection support (session tokens, all 3 directions)

Bug fixes since v0.2.0:
- EC-SRP5 server: fixed gamma parity (was 50% auth failure rate)
- EC-SRP5 server: use lift_x not redp1 for verification
- TCP send direction: server sends 12-byte status messages to client
- TCP both direction: TX loop injects status between data packets
- TCP data: send all zeros (no 0x07 header that MikroTik rejected)
- TCP disconnect detection: running flag set on EOF
- UDP multi-connection: unconnected socket accepts all source ports

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/server.rs

@@ -66,7 +66,11 @@ pub async fn run_server(
             if let Err(e) =
                 handle_client(stream, peer, auth_user, auth_pass, udp_offset, sessions, ecsrp5).await
             {
-                tracing::error!("Client {} error: {}", peer, e);
+                let err_str = format!("{}", e);
+                tracing::error!("Client {} error: {}", peer, err_str);
+                if err_str.contains("uth") {
+                    crate::syslog_logger::auth_failure(&peer.to_string(), "-", "-", &err_str);
+                }
             }
         });
     }
@@ -229,7 +233,14 @@ async fn handle_client(
         .await?;
     }
 
-    if cmd.is_udp() {
+    // Log auth success and test start
+    let auth_type = if ecsrp5_creds.is_some() { "ecsrp5" } else if auth_user.is_some() { "md5" } else { "none" };
+    let proto_str = if cmd.is_udp() { "UDP" } else { "TCP" };
+    let dir_str = match cmd.direction { CMD_DIR_RX => "RX", CMD_DIR_TX => "TX", _ => "BOTH" };
+    crate::syslog_logger::auth_success(&peer.to_string(), auth_user.as_deref().unwrap_or("-"), auth_type);
+    crate::syslog_logger::test_start(&peer.to_string(), proto_str, dir_str, cmd.tcp_conn_count);
+
+    let result = if cmd.is_udp() {
         run_udp_test_server(&mut stream, peer, &cmd, udp_port_offset).await
     } else if is_tcp_multi {
         let conn_count = cmd.tcp_conn_count;
@@ -285,7 +296,10 @@ async fn handle_client(
         run_tcp_multiconn_server(all_streams, cmd).await
     } else {
         run_tcp_test_server(stream, cmd).await
-    }
+    };
+
+    crate::syslog_logger::test_end(&peer.to_string(), proto_str, dir_str);
+    result
 }
 
 // --- TCP Test Server ---