Disable records instead of deleting them

A disabled record stays in Jarl with its ID, TTL and comment but is
left out of the zone; the zone file lists it as a comment. Web UI
toggle, jarl record disable|enable, record.disable|enable operations
and API endpoints. Database schema 5.

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

CHANGELOG.md

@@ -6,6 +6,23 @@ All notable changes to Jarl are documented here. The format follows
 
 ## [Unreleased]
 
+### Added
+
+- Disabled records: a record can be disabled instead of deleted. It stays
+  in Jarl with its ID, TTL and comment but is left out of the zone (the
+  zone file lists it as a comment), and enabling it puts it back exactly
+  as it was. Web UI: a Disable/Enable button on each record, disabled
+  records greyed out with a badge, a filter for them, and a count in the
+  zone list. CLI: `jarl record disable|enable` (by ID or by name, type and
+  data, `--ptr` for the PTR record, `--missing-ok`), `record list
+  --disabled`, and `disable:`/`enable:` entries for `jarl apply -f`. API:
+  `POST /records/{id}/disable|enable`, `POST
+  /zones/{zone}/records/disable|enable`, a `disabled` field on records,
+  `?disabled=` on record lists and `record.disable|enable` operations.
+  Validation checks the zone as it is served: the last NS record can't be
+  disabled, enabling a record is checked like adding it, and a disabled
+  record that a CNAME now blocks gets a warning. Database schema 5.
+
 ### Changed
 
 - Records table: names are no longer greyed out when they repeat the row