ui: F1 — populate OpenAlerts in baseView so nav badge updates everywhere

Flagged in review of 35dee98: the Alerts tab badge should show the
open count from any page, not just /alerts. baseView now takes the
request and queries store.ListAlerts(Status: "open") to fill
view.OpenAlerts on every page render. All call sites updated.

internal/server/http/ui_alerts.go

@@ -59,8 +59,7 @@ func (s *Server) handleUIAlerts(w stdhttp.ResponseWriter, r *stdhttp.Request) {
 	}
 	page.Counts = computeAlertCounts(s, r)
 
-	view := s.baseView(u)
-	view.OpenAlerts = page.Counts.Open
+	view := s.baseView(r, u)
 	view.Title = "Alerts · restic-manager"
 	view.Active = "alerts"
 	view.Page = page