Disable zones instead of deleting them

A disabled zone stays in Jarl with its records, options and history,
still editable, but named doesn't load it; enabling it serves it as it is
then. Signed zones, and zones another view shares, can't be disabled.
jarl zone disable|enable, the zone page's Disable/Enable button.
Database schema 7.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/server/present.go

@@ -16,7 +16,7 @@ import (
 )
 
 func (s *Server) presentZone(st *model.State, z *model.Zone, counts map[int64]recordCount) api.Zone {
-	out := api.Zone{Zone: *z, Display: dnsname.Display(z.Name), View: st.ViewName(z), Records: counts[z.ID].all, Disabled: counts[z.ID].disabled}
+	out := api.Zone{Zone: *z, Display: dnsname.Display(z.Name), View: st.ViewName(z), Records: counts[z.ID].all, DisabledRecords: counts[z.ID].disabled}
 	out.ZoneFile = render.ZoneFilePath(st, z, s.eng.Config().Paths)
 	if z.Type == model.ZonePrimary {
 		out.RName = dnsname.EmailFromMailbox(z.SOA.RName)