subpage: enabled state

Track and surface a subscription's enabled state from backend to frontend so the UI can show inactive subscriptions and use it in active-state logic.

Changes:
- sub/subService.go: track hasEnabledClient, set traffic.Enable, add Enabled to PageData and populate it in BuildPageData.
- sub/subController.go: include enabled in the page context.
- web/html/settings/panel/subscription/subpage.html: emit data-enabled attribute and render an "inactive" tag when disabled.
- web/assets/js/subscription.js: read data-enabled and include it in isActive() checks.

This ensures subscriptions with no enabled clients are marked inactive in the UI and excluded from being considered active.

sub/subController.go

@@ -138,6 +138,7 @@ func (a *SUBController) subs(c *gin.Context) {
 				"host":         page.Host,
 				"base_path":    page.BasePath,
 				"sId":          page.SId,
+				"enabled":      page.Enabled,
 				"download":     page.Download,
 				"upload":       page.Upload,
 				"total":        page.Total,