test(scale): cover traffic poll, ws payloads, ip-limit job, sub and xray config at 500k

The paths that run continuously in production had no scale coverage: the
5s traffic poll (AddTraffic with its auto-renew and depleted scans), the
websocket snapshot the job broadcasts while a browser is connected, the
10s ip-limit job (hasLimitIp LIKE scan + per-email settings parse), a
subscription fetch inside a huge inbound, and the full Xray config build.

New benchmarks reuse the XUI_SCALE_TEST / XUI_DB_TYPE gating and stay
log-only. Sizes default to 10k/100k; XUI_SCALE_SIZES=500000 raises the
ladder without editing code. seedScaleDataset writes inbounds, clients,
client_inbounds and client_traffics directly in one transaction instead
of SyncInbound, so a 500k seed takes seconds. XUI_SCALE_DB_PATH persists
the seeded SQLite file for manual smoke runs against a live panel.

internal/web/service/xray_config_scale_test.go

@@ -0,0 +1,66 @@
+package service
+
+import (
+	"encoding/json"
+	"fmt"
+	"testing"
+	"time"
+
+	"github.com/mhsanaei/3x-ui/v3/internal/database"
+	"github.com/mhsanaei/3x-ui/v3/internal/database/model"
+)
+
+// TestGetXrayConfigScale measures building the full Xray config (the path
+// every restart/reconcile takes) and, separately, how much of the per-inbound
+// settings rebuild is spent on indented vs plain JSON marshaling.
+func TestGetXrayConfigScale(t *testing.T) {
+	setupScaleDB(t)
+	svc := &XrayService{}
+	shapes := []struct {
+		name     string
+		inbounds int
+	}{{"single", 1}, {"spread50", 50}}
+
+	for _, n := range scaleSizes(t, 10000, 100000) {
+		for _, shape := range shapes {
+			t.Run(fmt.Sprintf("N=%d_%s", n, shape.name), func(t *testing.T) {
+				ds := seedScaleDataset(t, n, shape.inbounds)
+
+				const reps = 3
+				start := time.Now()
+				for range reps {
+					cfg, err := svc.GetXrayConfig()
+					if err != nil {
+						t.Fatalf("GetXrayConfig: %v", err)
+					}
+					if len(cfg.InboundConfigs) < shape.inbounds {
+						t.Fatalf("config has %d inbounds, want >= %d", len(cfg.InboundConfigs), shape.inbounds)
+					}
+				}
+				t.Logf("N=%-7d shape=%-8s GetXrayConfig=%v/run",
+					n, shape.name, (time.Since(start) / reps).Round(time.Millisecond))
+
+				var ib model.Inbound
+				if err := database.GetDB().First(&ib, ds.inboundIds[0]).Error; err != nil {
+					t.Fatalf("load inbound: %v", err)
+				}
+				settings := map[string]any{}
+				if err := json.Unmarshal([]byte(ib.Settings), &settings); err != nil {
+					t.Fatalf("unmarshal settings: %v", err)
+				}
+				start = time.Now()
+				if _, err := json.Marshal(settings); err != nil {
+					t.Fatalf("marshal settings: %v", err)
+				}
+				plain := time.Since(start)
+				start = time.Now()
+				if _, err := json.MarshalIndent(settings, "", "  "); err != nil {
+					t.Fatalf("marshal indent settings: %v", err)
+				}
+				indented := time.Since(start)
+				t.Logf("N=%-7d shape=%-8s settingsMarshal plain=%-9v indent=%v",
+					n, shape.name, plain.Round(time.Millisecond), indented.Round(time.Millisecond))
+			})
+		}
+	}
+}