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>

internal/web/static/assets/ui.js

@@ -193,11 +193,13 @@ export function problemsList(problems) {
   }));
 }
 
+// checkList shows named-checkconf's errors and warnings (not its routine
+// "loaded serial" lines).
 export function checkList(msgs) {
-  const errs = (msgs || []).filter((m) => m.error);
-  if (!errs.length) return null;
-  return h("ul", { class: "problems" }, errs.map((m) =>
-    h("li", { class: "error" }, h("strong", null, "named-checkconf: "), m.text, m.object ? h("span", { class: "where" }, m.object) : null)));
+  const shown = (msgs || []).filter((m) => m.error || !(m.text.startsWith("loaded serial") || m.text === "OK"));
+  if (!shown.length) return null;
+  return h("ul", { class: "problems" }, shown.map((m) =>
+    h("li", { class: m.error ? "error" : "warning" }, h("strong", null, m.error ? "named-checkconf: " : "named-checkconf warning: "), m.text, m.object ? h("span", { class: "where" }, m.object) : null)));
 }
 
 export function diffView(text) {