feat: balancer dashboard metrics + fix WebSocket Hijacker

internal/engine/engine.go

@@ -29,6 +29,7 @@ type Engine struct {
 	// Статистика для health endpoint
 	startTime      time.Time
 	routeRequests  atomic.Int64
+	routeFallbacks atomic.Int64
 	lastMetricTime atomic.Int64 // unix ts последней полученной метрики
 }
 
@@ -188,13 +189,19 @@ func (e *Engine) IncrementRouteRequests() {
 	e.routeRequests.Add(1)
 }
 
+// IncrementRouteFallbacks увеличивает счётчик fallback-запросов.
+func (e *Engine) IncrementRouteFallbacks() {
+	e.routeFallbacks.Add(1)
+}
+
 // HealthStats возвращает статистику для health endpoint.
 type HealthStats struct {
-	TotalNodes    int   `json:"total_nodes"`
-	HealthyNodes  int   `json:"healthy_nodes"`
-	RouteRequests int64 `json:"route_requests_total"`
-	UptimeSeconds int64 `json:"uptime_seconds"`
-	LastMetricTS  int64 `json:"last_metric_ts"`
+	TotalNodes     int   `json:"total_nodes"`
+	HealthyNodes   int   `json:"healthy_nodes"`
+	RouteRequests  int64 `json:"route_requests_total"`
+	RouteFallbacks int64 `json:"route_fallbacks_total"`
+	UptimeSeconds  int64 `json:"uptime_seconds"`
+	LastMetricTS   int64 `json:"last_metric_ts"`
 }
 
 // GetHealthStats возвращает текущую HealthStats (потокобезопасно).
@@ -209,11 +216,12 @@ func (e *Engine) GetHealthStats() HealthStats {
 		}
 	}
 	return HealthStats{
-		TotalNodes:    len(e.nodes),
-		HealthyNodes:  healthy,
-		RouteRequests: e.routeRequests.Load(),
-		UptimeSeconds: int64(time.Since(e.startTime).Seconds()),
-		LastMetricTS:  e.lastMetricTime.Load(),
+		TotalNodes:     len(e.nodes),
+		HealthyNodes:   healthy,
+		RouteRequests:  e.routeRequests.Load(),
+		RouteFallbacks: e.routeFallbacks.Load(),
+		UptimeSeconds:  int64(time.Since(e.startTime).Seconds()),
+		LastMetricTS:   e.lastMetricTime.Load(),
 	}
 }