feat(netinfra): add 18 VM DHCP reservations + PTR records [#420]

Pinned every production VM to its current ARP-observed LAN IP via DHCP
reservation. No IP changes — purely converts dynamic leases to fixed.
Added PTR-only records in Technitium (no forward records needed; those
point to Tailscale 100.x addresses).

DHCP failover sync triggered manually to netinfra-02. Live dhcpd.conf
pulled into repo.

Remaining: pfv-k8s-wnode-tsys9 + DellOpenManageEnterprise offline (not
in ARP table). Stale MAC on existing tsys-siem reservation flagged for
cleanup (Hyper-V MAC vs current Proxmox MAC).

💘 Generated with Crush

Assisted-by: Crush:glm-5.2

WORKING.md

@@ -7,7 +7,10 @@ A commit is blocked while any task below remains unchecked.
 
 (all done — session complete)
 
-- [x] Add ticket-closing policy: never close without user permission (AGENTS.md + meta template)
-- [x] Reopen #407 (KNELCredsManager not complete)
-- [x] Correct Vault understanding (deployed on Cloudron, not k8s)
-- [x] Create #420 (VM DHCP reservations + LAN reverse DNS)
+- [x] Build VM MAC→IP mapping from ARP table + Proxmox data
+- [x] Generate dhcpd.conf host reservations (18 production VMs, current IPs)
+- [x] Deploy reservations to netinfra-01 (syntax check passed, DHCP reloaded)
+- [x] Sync to netinfra-02 (manual trigger, confirmed)
+- [x] Add PTR records in Technitium (18 PTR-only records, verified)
+- [x] Pull updated dhcpd.conf into repo
+- [x] Create #421 (inotify DHCP sync, someday/maybe)