Link views from the zone list, add breadcrumbs and view colours

The view shown in the zone list and on the zone page now links to that
view. The zone page and changeset page get breadcrumbs, and the zone list
keeps its filters in the address so going back restores them. Views can
be given a colour (Views > Edit, `jarl view color`, PUT /views/{id}/color)
so zones of the same view are easy to spot; the colour is UI-only, kept
outside changesets, and needs no deploy.

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

docs/cli.md

@@ -300,6 +300,7 @@ jarl view create external --match-clients any
 jarl view order internal external
 jarl view update external --match-clients "!homelab,any"
 jarl view delete old [--cascade]
+jarl view color internal green                # web UI colour; "default" resets it
 
 jarl acl create homelab 192.168.1.0/24 10.10.0.0/16 localhost
 jarl acl update homelab --add 10.20.0.0/16 --remove 10.10.0.0/16