Fix zone list filtering and BIND warning display; add a views guide

- jarl zone list showed only primary zones. zone create binds its --type
  flag (default "primary") to the same variable as list's --type, so the
  default leaked into the list filter and hid hint, secondary and forward
  zones. list now has its own variable. TestListQueries runs list
  commands against a fake server and checks the filters they send.
- named-checkconf/named-checkzone messages are classified by the tool's
  exit code: on success, everything printed is a warning. Warnings such
  as 'both "recursion no;" and "allow-recursion" active' were shown as
  errors. The CLI, jarld check and the web UI now label them as warnings
  and skip the routine "loaded serial" lines.
- The zone_outside_view error points at --adopt-zones.
- docs/views.md: step-by-step split DNS for a server that has no views
  yet, tested on a copy of a stock Ubuntu 26.04 setup. Linked from the
  README, concepts and validation docs.

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

README.md

@@ -80,6 +80,7 @@ in `/etc/jarl/jarl.yaml` to reach it from your management network.
 | [docs/cli.md](docs/cli.md) | The `jarl` command line client |
 | [docs/api.md](docs/api.md) | REST API reference |
 | [docs/permissions.md](docs/permissions.md) | Users, tokens, grants and roles |
+| [docs/views.md](docs/views.md) | Split DNS: adding views to a server that has none |
 | [docs/acme.md](docs/acme.md) | Let's Encrypt DNS-01 with certbot and acme.sh |
 | [docs/validation.md](docs/validation.md) | Every check Jarl makes |
 | [docs/operations.md](docs/operations.md) | Backups, drift, failures, recovery, monitoring |