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>

internal/validate/zones.go

@@ -105,8 +105,8 @@ func (c *checker) checkZones() {
 				}
 			}
 		}
-		if !z.HasRecords() && len(c.zoneRecords[z.ID]) > 0 {
-			c.zoneProblem(z, Error, "zone_records_unmanaged", "%s zones can't have records managed by Jarl (they get their data from elsewhere); delete the %d records or change the type to primary", z.Type, len(c.zoneRecords[z.ID]))
+		if !z.HasRecords() && len(c.allRecords[z.ID]) > 0 {
+			c.zoneProblem(z, Error, "zone_records_unmanaged", "%s zones can't have records managed by Jarl (they get their data from elsewhere); delete the %d records or change the type to primary", z.Type, len(c.allRecords[z.ID]))
 		}
 	}
 }
@@ -188,6 +188,7 @@ func (c *checker) checkPrimary(z *model.Zone) {
 		c.zoneProblem(z, Info, "zone_name_slash", "zone names with '/' (RFC 2317) are supported, but the file name is escaped")
 	}
 	c.checkZoneRecords(z)
+	c.checkDisabledRecords(z)
 }
 
 // humanSeconds formats a duration in seconds as e.g. "1 day" or "12 hours".