Reverse DNS / PTR (IPv4 + IPv6)

[bcavnvidia]

Summary

Serve reverse-DNS / PTR records for both families from the single-zone authoritative resolver. The PTR row-mapper needs its own row type (the shared mapper force-casts to a single address type).

Dependencies

• Forward AAAA — re-attach instance records to the DNS view #2408 — builds on the instance-inclusive address source.

Additional Notes

• Stage: DNS-serving tail (deferred)
• Plan: IPV6_OVERLAY_PLAN/REVERSE_DNS_PLAN

[chet]

Delivered as part of the #2630 reverse-DNS work (this is effectively a duplicate). Reverse DNS / PTR for both IPv4 and IPv6 is served by the single-zone in-process resolver, with a dedicated PTR row type (DbPtrRecord + find_ptr_record) rather than the shared address mapper -- exactly the "PTR row-mapper needs its own row type" point here. Merged across #2691 (arpa→IP parse), #2711 (find_ptr_record / DbPtrRecord), #2719 (resolver routing), and #2720 (carbide-dns RData::PTR); reverse-zone provisioning landed in #2769. Moving to Verify.