B5 rehearsal fix: sing-box stats registration needs all three lists

The B5 full-stack rehearsal caught a silent accounting killer:
with the production switch set (inbound on, outbound off) the
generated v2ray_api stats block omitted the outbounds list, and
sing-box then registers NO counters at all — QueryStats answered
zero entries while real traffic flowed (A/B against the real core:
adding the list produced full user/inbound/outbound counters).

- builder: whenever the stats block is generated, emit inbounds,
  users and outbounds together; the gates now only decide whether
  the block exists
- master: enforce the inbound category gate at recording time in
  the agent traffic report (the whole-network accounting switch
  semantics: off period is never counted); onlines stay ungated
- golden gate test updated to the corrected contract

internal/web/controller/agent.go

@@ -684,8 +684,21 @@ func (a *AgentController) reportTraffic(c *gin.Context) {
 		jsonMsg(c, "Invalid request", err)
 		return
 	}
+	// ITEM6 B5 recording gate: a sing-box core registers counters
+	// only when every stats family is listed in its config, so the
+	// generated config can no longer omit a switched-off category
+	// (see the stats wiring in SingboxService). The whole-network
+	// accounting switches (settings.trafficStatsSwitches, the
+	// master switch on the Settings page) are therefore enforced
+	// here, at recording time: with the inbound category off
+	// (either direction), inbound totals and per-user traffic are
+	// accepted but not recorded — the off period is never counted,
+	// matching the switches' documented no-backfill semantics.
+	// Online presence is not traffic accounting and stays ungated.
+	sw := a.singboxService.GetTrafficStatsSwitches()
+	recordInbound := sw.InboundUplink && sw.InboundDownlink
 	db := database.GetDB()
-	if agent.NodeID != nil {
+	if recordInbound && agent.NodeID != nil {
 		for _, ib := range req.Inbounds {
 			if ib.Tag == "" || ib.Up+ib.Down <= 0 {
 				continue
@@ -699,15 +712,17 @@ func (a *AgentController) reportTraffic(c *gin.Context) {
 		}
 	}
 	var clientTraffics []*xray.ClientTraffic
-	for _, u := range req.Users {
-		if u.Email == "" || u.Up+u.Down <= 0 {
-			continue
+	if recordInbound {
+		for _, u := range req.Users {
+			if u.Email == "" || u.Up+u.Down <= 0 {
+				continue
+			}
+			clientTraffics = append(clientTraffics, &xray.ClientTraffic{
+				Email: u.Email,
+				Up:    u.Up,
+				Down:  u.Down,
+			})
 		}
-		clientTraffics = append(clientTraffics, &xray.ClientTraffic{
-			Email: u.Email,
-			Up:    u.Up,
-			Down:  u.Down,
-		})
 	}
 	if len(clientTraffics) > 0 {
 		if _, _, err := a.inboundService.AddTraffic(nil, clientTraffics); err != nil {