feat(monitoring): attribute SaaS citations by registrable domain

Persist host/registrable_domain/site_key on monitoring article URL
aliases, populate them on desktop-publish completion, and use them in
the citation pipeline to count how often SaaS-published content
appears as a citation source. Expose a /citation-summary endpoint with
a 7/30-day window switch and surface the new source-share metrics in
the tracking dashboard.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

server/internal/tenant/transport/router.go

@@ -183,6 +183,7 @@ func RegisterRoutes(app *bootstrap.App) {
 	monitoring := tenantProtected.Group("/monitoring")
 	monitoringHandler := NewMonitoringHandler(app)
 	monitoring.GET("/dashboard/composite", monitoringHandler.DashboardComposite)
+	monitoring.GET("/citation-summary", monitoringHandler.CitationSummary)
 	monitoring.GET("/brands/:brand_id/questions/:question_id/detail", monitoringHandler.QuestionDetail)
 	monitoring.POST("/brands/:brand_id/collect-now", monitoringHandler.CollectNow)