fix(outbound): store subscription refreshes without trusting the row read

The refresh rewrote the whole row it read before a download whose length
the provider controls, so an admin's delete, disable or edit made in the
meantime was undone; Update had the mirror problem. Both now write only
their own columns, and a refresh of a row that was deleted or re-pointed
stores nothing.

Around the same path:
- the preview fetches without creating (and leaking) a scratch row, and
  Create keeps enabled=false instead of falling back to the column default;
- fetch errors name the host but not the subscription URL, which is a
  credential and ends up in the log and in lastError;
- each fetch closes its transport's idle connections;
- one document loads at most 2000 links, and the cut is reported;
- wireguard outbounds from a subscription always run on the userspace TUN;
- editing a subscription schedules an Xray reload like delete and move do.

internal/web/controller/xray_setting.go

@@ -565,6 +565,8 @@ func (a *XraySettingController) updateOutboundSub(c *gin.Context) {
 		jsonMsg(c, "Failed to update outbound subscription", err)
 		return
 	}
+	// enabled and prepend decide which outbounds are merged and where.
+	a.XrayService.SetToNeedRestart()
 	jsonObj(c, "", nil)
 }
 
@@ -630,19 +632,7 @@ func (a *XraySettingController) parseOutboundSubURL(c *gin.Context) {
 	allowPrivate := c.PostForm("allowPrivate") == "true"
 	allowInsecure := c.PostForm("allowInsecure") == "true"
 	userAgent := c.PostForm("userAgent")
-	// Use a throw-away service instance; it only needs the settingService for proxy.
-	svc := service.OutboundSubscriptionService{}
-	// We don't have a direct "fetch once" that returns without storing, so we
-	// temporarily create a disabled row, refresh it, then delete. Cleaner would
-	// be to expose a pure ParseURL on the service, but this keeps the surface small.
-	tmp, err := svc.Create("preview", rawURL, "", userAgent, false, 600, allowPrivate, false, allowInsecure)
-	if err != nil {
-		jsonMsg(c, "Failed to preview subscription", err)
-		return
-	}
-	obs, err := svc.Refresh(tmp.Id)
-	// best-effort cleanup
-	_ = svc.Delete(tmp.Id)
+	obs, err := a.OutboundSubscriptionService.Preview(rawURL, userAgent, allowPrivate, allowInsecure)
 	if err != nil {
 		jsonMsg(c, "Failed to fetch/parse subscription", err)
 		return