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/render/render.go

@@ -398,6 +398,12 @@ func renderZone(w *confWriter, s *model.State, z *model.Zone, p Paths, out *Outp
 	if v := s.ViewName(z); v != "" {
 		label += " [view " + v + "]"
 	}
+	if z.Disabled {
+		// Kept in Jarl (its zone file too, so enabling it is quick), not
+		// loaded by named.
+		w.write(fmt.Sprintf("%s// zone %s is disabled in Jarl: named doesn't load it.\n", tabs, namedconf.QuoteString(dnsname.Display(z.Name))))
+		return
+	}
 	w.begin("zone", z.ID, label)
 	if z.Comment != "" {
 		w.write(indentLines(commentBlock("//", z.Comment), indent))