Zone page: links to the same zone in the other views

The header says "also in VIEW" for every zone of the same name in
another view, linked or not, in the view's colour, keeping the open tab
where the other zone has it. The zone API gains in_views.

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

docs/api.md

@@ -363,7 +363,10 @@ In a linked zone ([views.md](views.md#linked-zones)), records carry
 (`PATCH /records/{id}`) and setting (`PUT .../rrsets/...`) take `"local":
 true` (this view only, an override) or `false` (shared; on an update or a
 set it makes this view's version every view's). Zones carry `link_group`
-and `linked_with` (the other views).
+and `linked_with` (the other views). Every zone in a view carries
+`in_views`: the zones of the same name in the other views, linked or not
+and of any type, in view order (`[{"id": 289, "view": "external", "type":
+"primary", "linked": true}]`).
 
 | Method | Path | Body |
 |--------|------|------|