feat(proxmox): add e1000e offload fix script for Intel NIC hang bug

Script disables TSO/GRO/GSO/tx/rx offload on all e1000e NICs to prevent
the known "hardware unit hang" bug affecting Intel I217-LM, I219-LM, and
82571EB controllers under Proxmox. Applies live + installs systemd
service for persistence.

Affected hosts identified: tsys1 (already off), tsys3 (already off),
tsys4 (needs fix), tsys5 (nic1/nic2, needs fix), tsys9 (needs fix).
tsys6/7 use Broadcom (bnx2/tg3), not affected.

Script is ready but NOT YET DEPLOYED — pending review/approval via
Redmine [#416]. Initial attempt to deploy did not execute properly.

Based on archive/provisioning/Dell/Server/fixeth.sh.
Refs: https://forum.proxmox.com/threads/e1000-driver-hang.58284/

💘 Generated with Crush

Assisted-by: Crush:glm-5.2

WORKING.md

@@ -5,6 +5,4 @@ A commit is blocked while any task below remains unchecked.
 
 ## Current Tasks
 
-- [x] Install iperf3 on all hosts + production VMs (persistent)
-- [x] Create reusable any-to-any perf test script
-- [x] Enable iperf3 systemd service on hosts for on-demand testing
+- [x] Create e1000e offload fix script (repo only, not deployed yet)