Sort numeric labels by value

Records, zones and findings now order all-digit labels numerically, so
reverse zones list 2 before 101. model.CanonicalLess is replaced by
model.NameLess; other labels keep byte order.

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

CHANGELOG.md

@@ -42,6 +42,14 @@ All notable changes to Jarl are documented here. The format follows
 
 ### Changed
 
+- Records, zones and validation findings sort numeric labels by value, so
+  `2.10.0.10.in-addr.arpa` comes before `101.10.0.10.in-addr.arpa` in the
+  web UI, the CLI and the rendered zone files. Names still group by label
+  from the right (subdomains stay under their parent); other labels keep
+  the old byte order (`host10` before `host2`). Zone files are rewritten
+  in the new order the next time they change; named doesn't care about
+  record order.
+
 - `cname_chain` no longer warns about one CNAME pointing at another (a
   service name at a host alias is common, and named answers the chain at
   once). A chain of three or more CNAMEs gets an info note that shows