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>

docs/concepts.md

@@ -133,7 +133,8 @@ RFC 1982 arithmetic.
 * **Views** are ordered; named uses the first view whose `match-clients` and
   `match-destinations` match. Once one view exists, named requires every
   zone to be in a view, so creating the first view offers to move existing
-  zones into it (`adopt_zones`).
+  zones into it (`adopt_zones`). See [views.md](views.md) for a split-DNS
+  walkthrough.
 * **Zones** have a type: `primary`, `secondary`, `stub`, `static-stub`,
   `forward`, `mirror`, `hint`, `redirect`, or `in-view` (share a zone from
   another view). Only primary zones have records in Jarl. The same zone name