Retire SR-IOV, NIC tuning and watchdog scripts to unused/

Checked against the live host. None of these are in service:

- sriov-enp4s0.service and set-ixgbe-vfmacs-enp4s0.sh target enp4s0f1np1,
  which no longer exists; sriov_numvfs is 0 on every port and the unit was
  never installed.
- nic-performance-tweaks.service was never installed either, though its
  interfaces do still exist, so it would work if reinstated.
- vm-watchdog.sh watches VMID 2801 "pfsense", which no longer exists.
- lxc-watchdog.sh still carries the upstream example targets: CT 100 and
  CT 101 on 192.168.31.0/24, a subnet that is not in use.

Neither watchdog is scheduled; there is no root crontab.

The watchdog config moves to unused/conf/ alongside them, so the scripts
resolve it unchanged from their new location.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

unused/nic-performance-tweaks.service

@@ -0,0 +1,16 @@
+[Unit]
+Description=NIC performance tuning for enp4s0f0np0, enp4s1f12np12 and vmbr0
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Type=oneshot
+ExecStart=/usr/sbin/ethtool -G enp4s1f12np12 rx 4096 tx 4096
+ExecStart=/sbin/ip link set enp4s1f12np12 txqueuelen 10000
+ExecStart=/usr/sbin/ethtool -G enp4s0f0np0 rx 4096 tx 4096
+ExecStart=/sbin/ip link set enp4s0f0np0 txqueuelen 10000
+ExecStart=/sbin/ip link set vmbr0 txqueuelen 10000
+RemainAfterExit=true
+
+[Install]
+WantedBy=multi-user.target