One-view tokens: local records in linked zones, zone lookup, view list

A token for one view of a linked zone (an ACME token for external)
couldn't add records: a new record was shared and reached the other
view. A new name and type is now local when the user may not change it
in the other views. A zone name in several views resolves to the only
one the user can see, and the error no longer names views they can't.
GET /views lists the views a user sees zones in (name, colour, count;
limited) without views:read.

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

internal/server/present.go

@@ -82,6 +82,22 @@ func presentView(st *model.State, v *model.View, colors map[int64]string) api.Vi
 	return api.View{View: *v, Zones: len(st.ZonesInView(v.ID)), Color: colors[v.ID]}
 }
 
+// limitedView presents a view to a principal without views:read who can
+// see zones in it (the zone list names the view anyway): its name and
+// colour, and how many of its zones they can see. nil when they see none.
+func limitedView(st *model.State, v *model.View, colors map[int64]string, p *auth.Principal) *api.View {
+	n := 0
+	for _, z := range st.ZonesInView(v.ID) {
+		if p.CanSeeZone(z.Name, v.Name) {
+			n++
+		}
+	}
+	if n == 0 {
+		return nil
+	}
+	return &api.View{View: model.View{ID: v.ID, Name: v.Name, Position: v.Position}, Zones: n, Color: colors[v.ID], Limited: true}
+}
+
 func presentACL(st *model.State, a *model.ACL) api.ACL {
 	used := engine.FindACLRefs(st, a.Name)
 	if used == nil {