feat(server): UDP listener, hub WebSocket, Gauges Prometheus

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

server/websocket/hub_test.go

@@ -0,0 +1,40 @@
+package websocket_test
+
+import (
+	"encoding/json"
+	"net/http/httptest"
+	"strings"
+	"testing"
+	"time"
+
+	wslib "github.com/gorilla/websocket"
+	"github.com/user/nanometrics/server/websocket"
+)
+
+func TestHubBroadcast(t *testing.T) {
+	hub := websocket.NewHub()
+	srv := httptest.NewServer(websocket.Handler(hub))
+	defer srv.Close()
+
+	url := "ws" + strings.TrimPrefix(srv.URL, "http") + "/ws"
+	conn, _, err := wslib.DefaultDialer.Dial(url, nil)
+	if err != nil {
+		t.Fatalf("dial: %v", err)
+	}
+	defer conn.Close()
+
+	time.Sleep(50 * time.Millisecond)
+
+	hub.Broadcast(map[string]string{"type": "test", "msg": "hello"})
+
+	conn.SetReadDeadline(time.Now().Add(time.Second))
+	_, data, err := conn.ReadMessage()
+	if err != nil {
+		t.Fatalf("read: %v", err)
+	}
+	var got map[string]string
+	json.Unmarshal(data, &got)
+	if got["msg"] != "hello" {
+		t.Errorf("attendu hello, eu %s", got["msg"])
+	}
+}